Comptometer Model K

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This full keyboard non-printing adding machine has a brown metal frame and mechanism with plastic keys. The eight columns of color-coded green and white octagonal keys include nine keys in each column. Odd-numbered keys are concave, even-numbered ones flat. Complementary digits are indicated. A row of subtraction levers is below the number keys. Digits in the running total appear in a set of nine windows in front of the keys. A red button is to the right of the keyboard releases the keyboard afer a partial keystroke error has been corrected. A metal zeroing lever is on the right side. A rubber cord attaches to the back. The on/off switch is on the front at the top right.
The machine is marked on the left corner of the top of the case: K350690. It is marked on the front and back sides: Comptometer.
According to “Date of Manufacturing by Serial Number. . .,” Lewiston, Idaho: Office Machine Americana, 2002 (relying on the NOMDA “Blue Book” for May, 1975), Felt & Tarrant introduced the Model K with serial number 350000 in 1934.
Currently not on view
date made
Felt & Tarrant Manufacturing Company
place made
United States: Illinois, Chicago
Physical Description
rubber (overall material)
plastic (overall material)
metal (overall material)
overall: 14.8 cm x 25 cm x 32.2 cm; 5 13/16 in x 9 27/32 in x 12 11/16 in
ID Number
maker number
catalog number
accession number
Credit Line
Gift of Myron R. Smith
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Adding Machines
Data Source
National Museum of American History


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