Comptometer

Dorr E. Felt (1862-1930) built the prototype of a key-driven calculating machine using a wooden macaroni box as a case in 1885. In 1887 he obtained a patent, co-founded the Felt & Tarrant Manufacturing Co., and sold the first few Comptometers. An 1888 article on the Comptometer stated the "accuracy and durability of the machine have been thoroughly tested in the actuary's department of the United States Treasury at Washington, where one is in constant use." (Scientific American, Oct. 27, 1888) About 700 Comptometers were manufactured by late 1891. A June 1892 ad said Comptometers were "Now in use in hundreds of Banks and Counting Rooms."

An April 1895 ad noted Comptometers were "in use in over a thousand Counting Rooms and in the offices of six Governments" and "Over fifty have bought a second after buying a first." Assuming every serial number was used, about 2300 Comptometers had been produced by late 1896. A December 1900 ad explained Comptometers were "in hundreds of railroad and insurance offices" and "used by accountants and engineers in all lines of business." The ad also stated "in the US Navy Department over 85 Comptometers are used in engineering computations" and "nearly one thousand manufacturing and commercial firms after buying one Comptometer have ordered a second one and scores have purchased and used in their accounting rooms from 10 to 25 each."

Comptometers with wood cases were produced for about 16 years, from 1887 through 1903, after which cases were made of metal. The total number of wood-cased units manufactured did not exceed about 6300. Average annual production of wood-cased Comptometers increased from about 155 during the first 4.5 years (mid 1887-1891), to (at most) about 320 during the next five years (1892-96), and then to about 570 during the final seven years (1897-1903).