Comptometer Model J With Operator's Lock

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This full keyboard key-driven non-printing adding machine has eight columns of keys. These are colored white and green, with digits and complementary digits. Keys for odd digits are concave, those for even ones are flat. Key stems become taller going from front to back. The mechanism has a steel cover painted brown. Decimal markers, number wheels, and subtraction levers are at the front of the machine, and a zeroing crank is on the right side. The holes showing the nine number wheels are covered with clear plastic. A red button above the keyboard on the right, and a black knob with an arrow on it is above the keyboard on the left.
The machine is marked to the left of the keyboard with serial number J279,961. It is marked across the front of the machine: Comptometer. It is marked on a metal plaque on top of the machine in back of the keyboard: TRADE COMPTOMETER MARK. It is also marked there with a series of patent dates, the last of which is: NOV.2.20. It was received with a metal tag that reads: 14.
The Model J Comptometer was introduced by Felt & Tarrant Manufacturing Company of Chicago in 1926. Improved design and construction reduced the effort of operating the keys, compared to earlier models. This model also featured a operator’s lock, which locked the Comptometer so that new data could not be entered when a calculation was entered. Rotating the black knob so that the arrow points to the front locked the machine. This example came from the collection of Felt & Tarrant Manufacturing Company, and was given to the Smithsonian by the successor company, Victor Comptometer Corporation.
References: U.S. Patent 1,927,856 (granted September 26, 1933).
Felt & Tarrant, Accession Journal, 1991.3107.06.
Currently not on view
date made
Felt & Tarrant Manufacturing Company
place made
United States: Illinois, Chicago
Physical Description
metal (overall material)
plastic (overall material)
overall: 13.5 cm x 24 cm x 37.2 cm; 5 5/16 in x 9 7/16 in x 14 21/32 in
ID Number
maker number
catalog number
accession number
Credit Line
Gift of Victor Comptometer Corporation
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Adding Machines
Data Source
National Museum of American History


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