Monroe Model KA 160 Calculating Machine

In 1921 the Monroe Calculating Machine Company expanded its offerings to include calculating machines of several different capacities, selling the new machines as the model K. Soon thereafter, it began to sell automatic or electrically powered machines. This is an example of Monroe’s first electrically powered model, the KA.
The full-keyboard non-printing modified stepped drum machine has a metal frame painted black, with rounded corners. The steel plate under the keyboard is painted green. Eight columns of black and white plastic concave keys are colored according to the place value of the digit represented, with a red clearance key at the bottom of each column. Rods between the rows of keys serve as decimal markers. They are painted the same green as the plate underneath them on one side and white on the other.
To the right of the number keys are two bars and three keys in a column. The bars are for addition and subtraction. One key clears the entire keyboard. The other two are set to determine whether or not the keyboard clears after each calculation. A metal lever and a metal knob are to the left of the keyboard. A crank for operating the machine fits into the right side. It rotates clockwise for addition and counterclockwise for subtraction. A black motor attached to the left side at the back can be used to drive the machine. It has an on-off switch.
Behind the keyboard is a carriage that has a row of 16 numeral dials for recording results and a row of eight numeral dials behind these in the revolution register. Two thin metal rods between the rows of windows carry decimal markers. A crank for shifting the carriage is at the front of the machine; a knob for lifting the carriage is to the right of the result register; and a crank for zeroing dials on the carriage is on its right side. The machine has four rubber feet and a black two-pronged electrical cord.
A mark on the front reads: MONROE (/) Calculating Machine Company (/) New York. The serial number, on the frame of the mechanism on the right side under the carriage is: A7530. A red tag attached to the object reads: PATENT DEPT. (/) #253. This is model #253 from the collection of the Patent Division of Burroughs Corporation.
Compare MA*334711, MA*304386, 1983.0831.1, and 1984.0682.05.
J. H. McCarthy, The American Digest of Business Machines, Chicago: American Exchange Service, 1924, p. 551.
J. H. McCarthy, The American Digest of Business Machines, Chicago: American Exchange Service, 1928, vol. 2, pp. 9-29 to 9-33.
Currently not on view
Object Name
calculating machine
date made
ca 1925
Monroe Calculating Machine Company
Physical Description
aluminum (overall material)
wood (overall material)
plastic (overall material)
steel (overall material)
overall: 19 cm x 50 cm x 40 cm; 7 15/32 in x 19 11/16 in x 15 3/4 in
place made
United States: New Jersey, Orange
ID Number
catalog number
maker number
accession number
Science & Mathematics
Calculating Machines
See more items in
Medicine and Science: Mathematics
Calculating Machines
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Burroughs Corporation
Additional Media

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