Monroe Calculating Machine (Model K-16?)

This full-keyboard manually operated, non-printing, modified stepped drum calculating machine has a crinkled metal exterior with rounded corners, painted light green. The green paint has worn away in some places to reveal black paint beneath. The steel plate underneath the keys is dark green.
The machine has eight columns of black and white plastic digit keys. Rods between the columns of keys that serve as decimal markers. They are painted white on one side and the same green as the plate under the keyboard on the other. Pushing a red key at the bottom of each column zeros that column of keys. The key stems are of uniform length. A metal lever is to the right of the keyboard and a metal knob to the left. Rotating a crank on the right side clockwise adds numbers entered, moving it counterclockwise subtracts.
The carriage behind the keyboard has a row of 16 numeral dials for recording results. Eight numeral dials in a row behind these serve as a revolution register. Two thin metal rods between the windows carry decimal markers. The 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 is on the right side of the carriage. The machine has four rubber feet. To the left of the keyboard is a metal knob with an arrow on it. This knob is painted green.
A mark on the front and back sides reads, in cursive writing, Monroe. The mechanism of the machine, inside the carriage on the right, has the serial number: K66367
Compare MA.334711, MA.307386, 1983.0831.01, and 1982.0682.05.
The date of this machine is a mystery. The model resembles the K-16 described in McCarthy’s 1924 American Digest of Business Machines. The serial number is one the NOMDA blue book would associate with 1926. However, the Monroe logo is of a form introduced in 1940, and the light green color is quite unlike other Monroe machines of the 1920s.
The machine was given to the Smithsonian by David G. Owen, a statistician in the Research Division of the Miami Heart Institute.
National Office Machine Dealer’s Association, Blue Book, May 1975, as compiled by Office Machine Americana, January, 2002.
U.S. Patent and Trademark Office, Trademark Registration #522928, Serial #71117235.
Accession file.
Currently not on view
date made
Monroe Calculating Machine Company
place made
United States: New Jersey, Orange
Physical Description
steel (overall material)
wood (overall material)
aluminum (overall material)
plastic (overall material)
overall: 19.6 cm x 44.5 cm x 39 cm; 7 23/32 in x 17 17/32 in x 15 11/32 in
ID Number
catalog number
maker number
accession number
Credit Line
Gift of David G. Owen
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Calculating Machines
Data Source
National Museum of American History


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