Monroe Model LA 200 Calculating Machine

This portable, full-keyboard, electric, and non-printing modified stepped drum calculating machine has a gray steel case and gold and white color-coded plastic keys. The ten columns of keys have nine digit keys and one zeroing key in each column. The zeroing key is the opposite color from the rest of the keys in the column. Between the columns of keys, and under the plate, are metal rods visible through windows in the plate. These rods, painted green on one side and red on the other, serve as decimal markers.
To the right of the number keys are two red buttons, one of which is marked R (for use in repeated addition or subtraction), and a red clearance key. A crank on the right side rotates clockwise for addition and counterclockwise for subtraction. Above these are black subtraction and addition bars.
In back of the keyboard is the carriage, with 20 result dials and ten revolution register dials. Each revolution register dial is numbered from 0 to 9 in black and from 1 to 9 in red. Between the two registers on the carriage are two thin metal rods that carry green plastic decimal markers. A crank for clearing the carriage is on its right side. A carriage shift crank is at the front.
The machine may be operated automatically by plugging in the gray rubber two-pronged cord that extends from the back. The instrument has four metal feet, a gray plastic cover, and a brown leather-covered carrying case with key.
The machine is marked on the front: Monroe. No serial number found.
For related documentation, see 1986.0131.02. Date assigned is copyright date of the instructions.
This Monroe model L calculating machine is not only electrically operated (hence the A in the model number) but has a 20-digit capacity. Although it has a carrying case (hence the X in the model number), there are no extensible feet in the back, as on the L160-X.
Monroe Calculating Machine Company, Instruction Book Monroe Adding Calculator LA- Models, Orange, N.J., 1947 (1986.0131.02).
Currently not on view
Object Name
calculating machine
date made
Monroe Calculating Machine Company
Physical Description
rubber (overall material)
leather (overall material)
steel (overall material)
plastic (overall material)
overall: 18.5 cm x 37.5 cm x 35 cm; 7 9/32 in x 14 3/4 in x 13 25/32 in
place made
United States: New Jersey, Orange
ID Number
catalog number
accession number
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Calculating Machines
Data Source
National Museum of American History, Kenneth E. Behring Center


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