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Comptometer

The Comptometer is a mechanical calculator invented by American engineer Dorr E. Felt, patented in the United States in 1887, and recognized as the first commercially successful key-driven adding machine.^[1] It operated by directly pressing numbered keys to increment rotating wheels, enabling rapid arithmetic calculations without requiring a separate operating lever, a innovation that distinguished it from earlier crank-driven devices.^[2] Felt's prototype, built in 1885 in Chicago, Illinois, laid the groundwork for its production starting in 1888 by the Felt & Tarrant Manufacturing Company, which marketed it as an essential tool for office accounting and bookkeeping.^[3] Key features of the Comptometer included vertical columns of keys numbered 1 through 9 for each decimal place, with an automatic carry-over mechanism powered by helical springs that ensured accurate addition across digits.^[1] It supported not only addition but also subtraction (via the nine's complement method), multiplication (through repeated additions), and division (using reciprocal techniques), making it versatile for business applications.^[4] Skilled operators could enter multiple digits simultaneously using all ten fingers, achieving speeds far surpassing manual calculation, and the device featured a clearing lever to reset totals to zero.^[2] Early models, such as the Model A introduced around 1904, had 8 to 12 columns for handling numbers up to billions, with later variants accommodating specialized needs like currency conversions or imperial measurements.^[3] Over its production run, which continued into the early 1970s, the Comptometer evolved significantly; for instance, the 1913 Model E introduced controlled key actions to prevent errors, while the 1934 Model K added an electric motor for powered operation, and the 1939 Model M incorporated zero suppression for cleaner readouts.^[3] The company rebranded as the Comptometer Corporation in 1957, and after merging with Victor Adding Machine Company in 1961 to form Victor Comptometer Corporation, production shifted overseas, with British manufacturing under Bell Punch Company until the rise of electronic calculators rendered it obsolete.^[2] Its impact was profound, establishing a profession of "Comptometer operators"—often women trained in dedicated schools—and revolutionizing office efficiency by reducing calculation times in accounting from hours to minutes, influencing the broader development of business machines until the advent of computers in the late 20th century.^[4]

Overview and Operation

Design Principles

The Comptometer employed a key-driven mechanism that allowed operators to perform calculations directly through finger pressure on the keys, eliminating the need for a separate crank or lever to transfer entries into the register. This design featured multiple vertical columns—typically nine or more—each containing keys numbered from 1 to 9, enabling direct entry of digits into specific place values (units, tens, hundreds, etc.) without requiring sequential digit-by-digit input or manual carrying over between columns. Instead, the mechanism relied on parallel gear engagement across columns, where pressing a key in a given column immediately actuated the corresponding place value, with automatic carry propagation handled mechanically if a total exceeded nine in any dial.^[5]^[6] At its core, the Comptometer's mechanical system consisted of rocking segment levers, pinion gears, and result dials that facilitated the accumulation of values for addition and subtraction. Each key depression rocked a segment lever, which engaged a toothed pinion gear on a common shaft, advancing the associated result dial—a numbered wheel visible through a window—by the key's value (e.g., the "5" key rotated the dial five units). For subtraction, a mode selector reversed the gear direction, allowing negative increments on the dials. This setup ensured reliable, error-resistant operation through interlocks that prevented multiple keys per column from engaging simultaneously.^[5]^[6] A key innovation was the full-keyboard layout, which permitted simultaneous multi-digit entry across columns using multiple fingers, vastly improving efficiency for business computations like ledger balancing. Patented by Dorr E. Felt in 1887 (US Patent 366,945), this design enabled skilled operators to achieve speeds of up to 100 operations per minute by entering entire numbers in a single coordinated keystroke.^[6]^[5]^[7] Unlike earlier devices such as the Pascaline, which required sequential entry of digits starting from the highest place value and manual crank turns for each step, the Comptometer's parallel processing per column streamlined operations, making it particularly suited for rapid, repetitive additions in commercial settings without operator intervention in carries.^[5]^[8]

Usage and Mechanisms

The Comptometer is operated by depressing numbered keys on its keyboard to input values, with pressing and releasing the keys directly engaging the internal gear mechanisms to advance the result dials. For basic addition, the operator selects the appropriate digit keys in each column corresponding to the number's place values, allowing simultaneous depression of multiple keys across columns for efficiency; keys marked with larger numerals (1 through 9) are used, though higher values like 6-9 may require repeated or combined strokes in early models, while later designs support direct entry up to 9. Once keys are fully depressed and released, the dials increment by the entered amount with automatic carry-over.^[9]^[3] Subtraction is performed indirectly through the addition of complementary digits, utilizing the smaller numerals printed on the keys, which represent the 9's complement of the desired subtractend minus one to account for borrowing. For example, to subtract 7 from a total, the operator depresses the key marked with small 2 (since 9-7=2, adjusted to 2 for the borrow), along with corresponding keys for other digits, then activates a subtraction cut-off lever if available to prevent erroneous filling of leading digits with 9s; the keys are depressed and released as in addition to update the dials negatively. This method demands familiarity with complements to avoid errors, and the machine's interlocks in models from the 1910s onward ensure that only valid key combinations are processed.^[9]^[3] Multiplication relies on repeated addition, where the multiplicand is entered and added iteratively for each digit of the multiplier, with the operator shifting the entry position via a carriage or manual alignment for place values; on duplex keyboards introduced around 1904, multiple digits of the multiplier can be entered simultaneously across columns for faster operation. Division employs a trial-and-error approach using complementary subtraction, starting with an estimate of the quotient digit, subtracting multiples via the complement method, and adjusting based on the remainder until it is reduced below the divisor, often requiring a non-add key to clear partial errors mid-process. Proficiency in these methods typically necessitates operator training, as the processes involve mental tracking of carries, remainders, and complements.^[9]^[3] Later Comptometer designs incorporated error detection features such as the "Controlled Key" mechanism from 1913, which locks the operating lever until all depressed keys are fully engaged, preventing incomplete entries, and a dedicated non-add key to reset erroneous inputs without affecting the total. Additional interlocks prohibit simultaneous depression of multiple keys in the same column, reducing invalid operations, while visual or tactile signals in 1920s models alert operators to start-from-clear conditions. These safeguards improved reliability in high-volume accounting tasks.^[3] The keyboard layout consists of vertical columns for each decimal place with rows for digits 1-9, facilitating touch-typing with both hands to minimize eye movement and fatigue during prolonged use in office environments like payroll processing, inventory tracking, and billing. Training programs, established from 1905, involved dedicated schools offering three-month courses in mechanical arithmetic, emphasizing daily practice to build speed—such as 20 minutes per day over 60 days for optimal skill development—and covering applications in trade-specific scenarios, producing thousands of proficient operators annually by the 1920s. Proper ergonomics, including seated posture and hand positioning, were taught to sustain productivity without strain.^[9]^[10]

History

Invention and Origins

Dorr Eugene Felt was born on March 18, 1862, in Boscobel, Wisconsin.^[11] As a teenager, he apprenticed in a machine shop in Beloit, Wisconsin, where he developed skills as a self-taught mechanic and machinist.^[12] While employed in a Chicago workshop operating a planer, Felt became inspired by existing mechanical calculators like the arithmometer, prompting him to envision a more efficient device for rapid business computations.^[13] In late 1884, during a Thanksgiving holiday, Felt constructed his first prototype in his Chicago workshop, fashioning the frame from a macaroni box, the keys from wooden meat skewers, and springs from rubber bands, with additional parts like staples for assembly.^[14] This manual effort, completed over several months despite initial plans for a quicker build, demonstrated a basic adding mechanism using lever actions to increment numbered wheels.^[13] The design marked an early conceptual shift from crank-operated calculators, such as the Thomas arithmometer, to a direct key-driven system that allowed faster number entry and reduced operator errors in office settings.^[15] Felt's invention drew on prior devices, including the keyboard layout of Thomas Hill's 1857 U.S. Patent 18,692 for a key-driven adding machine and the gear-based principles of Blaise Pascal's 1642 Pascaline, the earliest mechanical calculator.^[16] On July 19, 1887, the U.S. Patent Office granted Felt U.S. Patent 366,945 for his "Adding-Machine," which detailed the core mechanism of independent keys actuating toothed segments that advanced result dials.^[6] Facing challenges in securing funding and refining the prototype for reliability, Felt sought visibility by demonstrating an improved version at the 1893 World's Columbian Exposition in Chicago, where it attracted potential investors and highlighted its potential for commercial business use.^[17]

Early Production and Comptograph

Following the patenting of the Comptometer in 1887, Dorr E. Felt entered into a partnership with Robert Tarrant on November 28, 1887, which was formalized as the Felt & Tarrant Manufacturing Company on January 25, 1889, enabling the shift from prototypes to commercial production.^[18] Initial manufacturing efforts were limited, with hand-built wooden-cased Comptometers produced in small quantities starting around 1888; average annual output reached approximately 155 units during the first 4.5 years from mid-1887 to 1891.^[19] Full-scale production commenced in 1889 under the new partnership, focusing on key-driven adding machines for office use.^[2] A significant advancement came with the introduction of the Comptograph in 1889, which incorporated a printing mechanism to record calculations on paper tape, facilitating auditing and verification in financial settings.^[20] This variant was patented on June 11, 1889, under U.S. Patent 405,024, filed by Felt on January 19, 1888.^[21] The device targeted banks and offices requiring documented computations, with the first 25 units hand-built and sold primarily to banking institutions.^[20] The inaugural sale occurred in December 1889 to the Merchants & Manufacturers National Bank in Pittsburgh, Pennsylvania, for $350, marking the debut of a practical printing adding machine.^[22]^[23] Production techniques evolved rapidly to meet demand, with early Comptometers featuring wooden frames for lighter weight, though these were prone to wear.^[24] By 1900, the company began transitioning to more durable metal frames, completing the shift by 1903 to enhance longevity and scalability in manufacturing.^[25] Marketing emphasized the device's speed and reliability, positioning it as capable of performing thousands of additions per hour to streamline accounting tasks.^[26] By 1890, output for the improved Comptograph reached 100 units, incorporating automatic printing features.^[20]

Competition and Market Growth

The Comptometer faced significant competition from other mechanical calculators emerging in the late 19th and early 20th centuries. The Burroughs Adding Machine, introduced in 1888 and featuring printing capabilities by the early 1890s, became a direct rival by offering listing functions that the non-printing Comptometer lacked initially.^[27] In response, Felt & Tarrant introduced the Comptograph in 1889, a printing variant of the Comptometer, though it struggled to match Burroughs' market success.^[25] Another key competitor was the Millionaire calculator, patented in 1893 by Otto Steiger and marketed for direct multiplication, appealing to users needing advanced operations beyond the Comptometer's primary addition focus.^[28] Market penetration grew rapidly in the United States, with the Comptometer adopted widely in offices and accounting departments by the early 1900s due to its speed and reliability in basic arithmetic tasks.^[29] By the 1910s, international expansion occurred through sales agents in Europe, where the machine gained traction for commercial use despite initial focus on the U.S. market.^[30] The 1920s marked a peak in dominance, as the Comptometer became a standard tool in back-office accounting, supported by annual training of around 10,000 operators in U.S. schools established in 1905.^[5] Growth was further propelled by World War I demand for logistics and production calculations, contributing to a postwar sales surge after the introduction of the improved Model F in 1915.^[31] Challenges included patent disputes, such as Felt & Tarrant's successful 1910s lawsuit against Burroughs for design infringement on their key-driven calculator, which resembled the Comptometer and led to modifications in Burroughs' models.^[32] Earlier efforts in the 1890s involved defending against imitators through patent enforcement, protecting the core mechanism.^[3] The 1929 stock market crash and ensuing Great Depression reduced overall demand for office equipment, impacting sales across the mechanical calculator industry as businesses cut costs amid widespread economic contraction.^[33]

Manufacturers

Felt & Tarrant Manufacturing Company

The Felt & Tarrant Manufacturing Company was founded in 1889 by inventor Dorr E. Felt and businessman Robert Tarrant in Chicago, Illinois, to mass-produce the Comptometer, Felt's patented key-driven adding machine. Incorporated on January 25, 1889, the company focused on commercializing this innovative device, which represented a significant advancement in mechanical calculation tools for business and accounting applications. From its inception, the firm emphasized efficient production and marketing, quickly establishing itself as a leader in the emerging office machinery sector.^[34]^[3]^[35] Operations expanded rapidly in the early 20th century, with the company constructing a dedicated factory at North Paulina Street in Chicago in 1908, which underwent further enlargements to support growing demand. By the 1910s and 1920s, Felt & Tarrant had developed a robust international presence, exporting Comptometers to markets in Europe, Asia, Australia, and beyond, including shipments to Denmark as early as 1916. The firm also implemented sales training programs to equip operators and salespeople, enhancing adoption among accountants and businesses worldwide. Production scaled impressively, with over 40,000 units of the Model F alone sold between 1915 and 1920, underscoring the company's commercial success. A UK subsidiary, Felt & Tarrant Ltd., was later established to handle assembly and distribution in Europe.^[3]^[36]^[15] Under Felt & Tarrant's stewardship, several key innovations enhanced the Comptometer's design and functionality. In 1904, the company introduced the Model A, featuring a durable metal casing that improved portability and protection compared to earlier wooden models, while allowing for duplex operation across multiple columns. By the 1920s and into the 1930s, variants incorporating electric motors were developed, such as the Model K in 1934, which automated clearing and reduced manual effort for high-volume calculations. These advancements, building on Felt's original patents, solidified the Comptometer's reputation for speed and reliability in office environments.^[37]^[3] Dorr E. Felt served as president and driving force behind the company until his death from a stroke in 1930, after which management transitioned to family members and key executives like Joseph A. V. Turck, who contributed over 40 patents to further refinements. This period of independent operation, from 1889 through the mid-20th century, marked the company's peak as an innovator in mechanical computing, before later corporate changes.^[15]^[3]^[18]

Successor Companies and Mergers

In 1957, the Felt & Tarrant Manufacturing Company rebranded as the Comptometer Corporation to reflect its primary product and pursue diversification under new management, while continuing production of mechanical Comptometers in the United States.^[38]^[3] This entity maintained operations through the 1960s, focusing on mechanical calculators amid growing competition from electronic devices, but U.S. production of traditional Comptometers ceased by the mid-1970s as the market shifted to electronics.^[15] In 1961, the Comptometer Corporation merged with the Victor Adding Machine Company, forming the Victor Comptometer Corporation, which integrated Comptometer's full-keyboard designs with Victor's adding machines and expanded to 18 plants across the U.S. and Canada by 1968.^[39]^[3] In 1969 it sold its electronics division to Nixdorf Computer AG of Germany, signaling a retreat from advanced calculator development.^[39] At the decade's end, Victor Comptometer was acquired by Kidde Inc. of New Jersey in 1977, leading to relocation of production and eventual rebranding as Victor Technology LLC, which continues in office electronics but no longer under the Comptometer name.^[40] Internationally, the Comptometer Corporation sold its British operations to the Bell Punch Company in 1960, granting rights to the "Comptometer" trademark in the UK and resolving prior licensing disputes through this transfer.^[41]^[42] In 1961, Bell Punch amalgamated these assets with its Sumlock calculator division to form Sumlock Comptometer Ltd, which produced mechanical models under the Comptometer branding while pioneering electronic calculators like the ANITA series starting that year.^[41] The company operated until 1973, when it was acquired by Rockwell International, which wound down calculator production by around 1976, after which the Sumlock Comptometer trademarks lapsed or integrated into broader electronics portfolios.^[41]

Model Evolution

Early Models (Pre-1910)

The earliest Comptometers, known as the "woodies," were hand-built from 1887 to 1903 and encased in simple pine boxes. These prototypes featured a 10-digit capacity and were restricted to addition operations, as the mechanism relied on sequential key presses to advance geared wheels in the register. Approximately 6,500 units were produced during this period, reflecting the handmade nature of production by the Felt & Tarrant Manufacturing Company in Chicago.^[25]^[43] In 1904, the company introduced the Model A, marking the transition to an all-metal casing that significantly enhanced durability over the wooden designs. This model expanded the result capacity to 12 digits, allowing for more complex calculations in business applications, while maintaining the core lever-operated adding mechanism. Priced at $275, the Model A represented a commercial refinement aimed at office use, with improved key action for faster entry.^[3]^[25] Subsequent evolutions included the Models B, C, and D, produced from 1907 to 1912, which built on the metal construction to refine ergonomics and functionality. The Model B featured a curved front panel for better visibility of the register, while the Model C, introduced in 1909, featured composite keys for improved action, with subtraction via the nine's complement method. The Model D (1907) was a variant omitting the Controlled Key for cost savings, maintaining standard column capacities. Overall, pre-1910 production across these early models totaled over 20,000 units, underscoring the growing adoption of mechanical calculators in early 20th-century commerce.^[25] A key limitation of all pre-1910 models was the absence of printing capabilities, requiring manual transcription of results from the mechanical register dials. Operations were performed exclusively via a manual operating lever, which advanced the carriage after key entries, without any automated or electric assistance. These designs prioritized reliability and speed for addition and basic subtraction but lacked versatility for multiplication or division beyond operator techniques.^[2]^[25]

Mid-20th Century Models (1910s-1940s)

The Mid-20th century marked a period of refinement and functional expansion for the Comptometer, with models E through K introducing mechanisms for error prevention, ergonomic improvements, and eventual electrification to enhance operational efficiency in office environments. The Model E, produced from 1913 to 1915, was a transitional design that debuted the Controlled Key mechanism, an elaborate system designed to detect incomplete or erroneous keystrokes by locking the machine until the error was corrected, thereby preventing calculation mistakes.^[3] This model typically featured 10 or 11 columns for digit entry, allowing for handling of numbers up to 11 digits, and weighed approximately 21 pounds.^[3] With around 7,700 units manufactured, the Model E gained traction in wartime administrative settings during World War I, where it supported rapid data processing in offices staffed increasingly by women operators replacing men at the front.^[25] Succeeding the Model E, the Model F, built from 1915 to 1920, refined the Controlled Key with recalibration for smoother operation while eliminating bulky interference guards, contributing to over 40,000 units produced and a slight weight reduction to about 20 pounds.^[3] It maintained 10 or 11 columns and remained fully manual, enabling skilled operators to achieve addition speeds of up to 150 entries per minute through efficient key-pressing techniques.^[25] By the 1920s, the Model H (1920-1927) and Model J (1928-1938) further advanced usability with features like a start-from-clear signal providing visual, audible, or tactile feedback to ensure operations began from zero, alongside lighter key actions and green-and-white keytops for better visibility.^[3] These models supported 8 to 13 columns, with the J variant producing over 100,000 units and weighing around 25 pounds, standardizing subtraction via the nine's complement method.^[25] The compact ST (Super Totalizer) variant, derived from the Model J in the 1930s, catered to mobile sales teams with its dual-register design for accumulating subtotals and grand totals in 10 or 11 columns, weighing 27 pounds for portability.^[3] The pinnacle of this era's innovations came with the Model K, introduced in 1934 and produced until 1950 as the first fully electric Comptometer, featuring a motor-driven mechanism and a tilted keyboard for reduced operator fatigue, with production peaking at about 32,800 units amid the Great Depression despite high costs exceeding $1,000 per machine.^[3] Capable of 12 or 13 digits and weighing 24 pounds, it represented a shift toward powered operation while retaining core mechanical principles.^[25] Across these models, overall advancements included expanding column capacities from 10 to up to 13 for larger computations and progressive weight reductions toward 25 pounds, facilitating broader adoption in professional settings without sacrificing durability.^[3]

Post-WWII and Electronic Models

Following World War II, the Comptometer saw refinements in its mechanical designs to meet the demands of expanding postwar office environments, emphasizing greater durability and ease of integration with other business equipment. The Model M, introduced in 1939 and produced until 1950, featured a rounded pressed-metal casing painted in mid-green, along with improvements such as leading-zero suppression via numeral wheel shutters and latching subtraction buttons for reduced operator errors.^[3]^[25] These enhancements contributed to its reliability, with over 114,000 units manufactured between serial numbers 400,000 and 514,367.^[25] A wartime variant, the Model WM, was developed during the 1940s to conserve metal, incorporating thinner parts with perforations that made it lighter while retaining the core specifications of the Model M, including 8 to 12 columns for multi-digit operations.^[25] The final pure mechanical Comptometer models, such as the Model 3D11 produced from 1950 to 1961, further bolstered durability through features like a single key for multiplication and division, which automatically reset the controlled-key mechanism to prevent carry-over issues.^[3] These machines were engineered for sustained use in high-volume accounting tasks, with some early variants remaining operational over a century later, underscoring their robust construction.^[3] Additionally, postwar models like the electric Model 992, introduced in the 1950s, incorporated motor drives akin to those in electric typewriters, facilitating smoother integration into typewriter-equipped workstations and lighter key action for prolonged operator sessions.^[3] The transition to electronic models began with the ANITA series, developed by Sumlock Comptometer Ltd. as the successor to Felt & Tarrant. The ANITA Mark VII, launched in late 1961, marked the world's first all-electronic desktop calculator, utilizing cold-cathode vacuum tubes and a 13-digit Nixie-type tube display for real-time results on a full keyboard layout reminiscent of mechanical Comptometers.^[44] It supported four basic arithmetic functions with instantaneous addition and subtraction, weighing approximately 30 pounds and priced around £250.^[44] The ANITA Mark VIII, introduced simultaneously in 1961 and entering full production in 1962, offered a 12-digit display and added an optional plug-in transistorized memory unit for storing intermediate results, combining cold-cathode tubes with limited vacuum tubes and transistors for improved reliability.^[45] Subsequent advancements in the series included the ANITA Mark 10, released in 1965, which maintained a 12-digit full-keyboard design but incorporated enhanced cold-cathode tube logic with Dekatron counters and dual-mode operation for decimal and Sterling currency calculations, including direct conversion keys.^[46] Priced at about £480, it catered to international business needs during the UK's decimalization transition.^[46] Mechanical Comptometer production ceased in the mid-1970s, primarily in the UK under Sumlock, while electronic variants continued under the Victor Comptometer Corporation into the 1980s, evolving with transistorized and integrated circuit technologies before the rise of affordable handheld calculators.^[3]^[47]

Legacy

Technological and Economic Impact

The Comptometer pioneered key-driven input mechanisms in mechanical calculators, allowing direct numerical entry without cranks or levers, which significantly advanced the mechanization of accounting processes. This innovation influenced subsequent office technologies, including cash registers and early electronic calculators, by establishing a standardized approach to rapid data processing that bridged manual computation and automated systems. By the early 20th century, it had become a cornerstone of office efficiency, enabling the separation of complex accounting tasks from routine bookkeeping and facilitating the growth of data-intensive business operations.^[48]^[49] Economically, the Comptometer transformed business efficiency by reducing calculation times by 50-75% compared to manual methods, allowing firms to process financial data in minutes rather than hours and produce timely reports that supported managerial decision-making. Its adoption by large corporations, such as banks and manufacturing enterprises, lowered operational costs—for instance, some institutions recouped machine expenses within 14 months through labor savings—and enabled the scaling of operations in expanding industries like finance and production. The device also spurred job creation, particularly for women entering the clerical workforce; by the late 1920s, over 100 training schools in the United States and 50 abroad were producing approximately 20,000 skilled operators annually, leading to an estimated 100,000 or more Comptometer operators by the 1930s who filled roles in accounting departments worldwide.^[29]^[50] Culturally, the Comptometer symbolized modernity in the interwar period, standardizing office workflows. Its dedicated training programs functioned as early vocational initiatives, professionalizing calculation skills and integrating women into white-collar employment, thereby reshaping workplace norms and gender dynamics in commerce. As a mechanical precursor to electronic computing, the Comptometer's legacy lies in its role as a transitional technology, sustaining production for decades and influencing the evolution from 19th-century mechanics to mid-20th-century digital systems.^[48]^[50]

Decline and Modern Relevance

The decline of the Comptometer began in the early 1960s with the emergence of electronic calculators, which offered greater speed, reduced noise, and lower long-term costs compared to mechanical devices. The ANITA Mark VII, released in 1961 by Sumlock Comptometer, represented one of the first all-electronic desktop calculators, signaling the transition away from mechanical computing tools. By 1968, Hewlett-Packard's HP-9100A introduced programmable electronic capabilities at a price point that undercut mechanical alternatives, accelerating the obsolescence of key-driven adding machines like the Comptometer. The profession of comptometer operation, once widespread in offices, sharply declined during the late 1960s as businesses adopted computers and data processing systems. Mechanical Comptometer production in the United States ceased in 1961 when Felt & Tarrant ended manufacturing, though Sumlock in the UK continued producing mechanical models into the mid-1970s. Globally, the phase-out of mechanical calculators was complete by around 1980, coinciding with the economic shift toward personal computers and software solutions such as spreadsheets—VisiCalc in 1979 marked the beginning of this era, enabling automated calculations that rendered manual devices unnecessary. Today, Comptometers hold modern relevance primarily as collectibles and historical artifacts, preserved in institutions like the Computer History Museum, which houses multiple examples to illustrate early mechanical computation. Restored units are occasionally demonstrated in steampunk-inspired settings or educational exhibits, showcasing their intricate gear mechanisms for audiences interested in pre-electronic technology. Their educational value lies in demonstrating the evolution of computational tools, providing hands-on insight into the history of arithmetic machinery.^[51]^[52] No revivals of mechanical Comptometer production have occurred post-2020, though the trademark rights are held by Victor Technology LLC, which uses the legacy branding for contemporary electronic calculators. Online simulations, such as the JavaScript-based emulator available on mechanical calculator enthusiast sites, allow virtual operation for research and demonstration purposes.^[53]^[54]

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D. E. FELT. ADDING MACHINE. No. 366,945 Patented July 19, 1887. we 71 to? n. PEIERS, Prinwumo n w. wa mn mn, o .c. (No Model.) 5 Sheets-Sheet 3'. D. E. FELT.Missing: Comptometer Dorr
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The Comptometer computing device became a great commercial success and was sold and used world-wide. As a result of Felt's experience as president of a large ...
[32]
Burroughs - Mechanical Calculators - Jaap's Scratch Pad
It was first made in 1911 and deliberately styled to resemble the Comptometer. The patent infringement court case filed by Felt & Tarrant forced them to change ...Missing: share | Show results with:share
[33]
Stock Market Crash of 1929 | Federal Reserve History
On Black Monday, October 28, 1929, the Dow declined nearly 13 percent. On the following day, Black Tuesday, the market dropped nearly 12 percent. By mid- ...
[34]
Felt & Tarrant Manufacturing Company - IT History Society
The Felt and Tarrant Manufacturing Company was founded to manufacture the Comptometer, invented by Dorr Eugene Felt and patented in 1887.Missing: capital $10000
[35]
Felt and Tarrant Manufacturing Company 1889 - 1957
1887 - Comptometer patented by Dorr Eugene Felt (1862-1930), the first practical and commercially successful adding machine, 1888 - manufacture of ...
[36]
[PDF] Dorr Felt Collection Felt and Tarrant Manufacturing Records
Felt opened Felt and Tarrant Manufacturing Company with Chicago businessman Robert. Tarrant in 1889; a large manufacturing facility in Chicago, out of which ...Missing: founding history
[37]
Comptometer Model A | National Museum of American History
The Comptometer Model A is a key-driven, non-printing adding machine with eight columns, color-coded keys, and a 'duplex' design, first produced in 1904.Missing: electric motor 1920s
[38]
Felt, Tarrant Changes Name - The New York Times
A seventy-year-old Chicago company has changed its name to honor the calculating machine that made it famous. The Comptometer Corporation is the new name ...
[39]
Victor Adding Machine Co. - Encyclopedia of Chicago
Victor Adding Machine made the first portable desk calculators. Between 1921 and 1925, Victor's annual sales jumped from less than $300,000 to nearly $2 million ...
[40]
Victor Adding Machine Co., est. 1918 - Made-in-Chicago Museum
Small, compact, easy to move anywhere. Precision-built, like fine watches. Strong and sturdy. Made by the World's Largest Exclusive Manufacturers of Adding ...
[41]
Bell Punch / Sumlock / Anita - Vintage Calculators
1961 - Sumlock Comptometer Ltd formed from the amalgamation of the British operation of Comptometer Corporation of Chicago, U.S.A., with the calculator ...
[42]
All Change at Bell Punch - Anita Calculators
Comptometer Corporation then contracted with Control Systems to have all its machines made by Control Systems in England and shipped back to the U.S.A. This ...
[43]
Dorr Felt - Computer Timeline
Interestingly, Felt's first patent in 1885 (USA Nr. 366945) would assign the invention to Foster and himself. The first practical model was ready in the ...
[44]
Anita Mk VII - Vintage Calculators
The ANITA Mk VII is a full-keyboard calculator with a 13-digit "Nixie" type tube display, and makes extensive use of cold-cathode vacuum tubes.
[45]
Anita Mk 8 - Vintage Calculators
This model and the Mk VII were the only electronic desktop calculators in the world for over two years, and many thousands were sold. Like the Mk VII it has a ...
[46]
ANITA Mk 10 - Anita Calculators
The ANITA Mk 10 is a 12-digit calculator with a full keyboard, decimal and Sterling capability, and direct £sd conversion, but it is a decimal machine at heart.Missing: portable | Show results with:portable
[47]
Victor
In 1961 the Comptometer Corporation merged with Victor to form the Victor Comptometer Corporation. Victor developed its mechanical calculators which sold ...
[48]
The Comptometer and the Burroughs: Two Early Office Machines ...
Between 1885 and 1915, the adding machine and calculator firmly established themselves in the marketplace and became essential elements in most business ...
[49]
A brief history of the numeric keypad - DOC
The idea was based on the Pasacline's mechanism, the layout of Thomas Mill's machine and a macaroni box. It was known as the Comptometer, a device with eight ...
[50]
The Comptometer Operator - John Wolff's Web Museum
Mar 20, 2011 · The Comptometer schools typically recruited young girls and (sometimes) men straight from school at about 16 years old. Training began with the ...Missing: 1890s | Show results with:1890s
[51]
Plastics Conservation: Comptometers and Patents
Apr 15, 2021 · The Comptometer is a calculating machine that was used prolifically in accounting firms, banks (seen in the 1938 film You Can't Take it with You), and even ...