Monroe Model LA5-160x Calculating Machine

Monroe Model LA5-160x Calculating Machine

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This full-keyboard, non-printing electric modified stepped drum calculating machine has a metal frame painted black, with a plate under the keyboard that appears to be unpainted. The eight columns of white plastic number keys have nine keys in each column. Below each column is a tenth white key used for zeroing. Between the columns of keys, and under the plate, are metal rods visible through windows in the plate that serve as decimal markers. To the right of the number keys are the subtraction and addition bars, two red buttons, and a red clearance button.
In back of the keyboard is the carriage, with 16 result dials and eight revolution register dials. A carriage shift crank is at the front. The machine has four rubber feet, and a gray rubber electric cord. It has no case and the feet are not extensible at the back.
A mark on the machine reads: MONROE (/) HIGH SPEED ADDING CALCULATOR. Another mark reads; PROPERTY U.S.N.BU.ORD. (/) CONTRACT NOO 1709 (/) U.S.N. NO 504487. A mark scratched on the inside of the carriage at the left reads: 273166.
Compare MA.334385.
The donor was a certified public accountant who had a collection of calculating machines. The date of manufacture and original cost ($375) are provided by him.
National Office Machine Dealer’s Association, Blue Book, May, 1975, as compiled by Office Machine Americana, January, 2002.
Monroe Calculating Machine Company, “Monroe High Speed Adding-Calculator,” Publication 780-A. This is a notebook with advertising descriptions of several Monroe calculating machines.
Accession file.
Currently not on view
Object Name
calculating machine
date made
Monroe Calculating Machine Company
Physical Description
metal (overall material)
rubber (overall material)
plastic (overall material)
overall: 16.4 cm x 27.2 cm x 27 cm; 6 15/32 in x 10 23/32 in x 10 5/8 in
ID Number
accession number
maker number
catalog number
Credit Line
Gift of William L. Jackson
See more items in
Medicine and Science: Mathematics
Calculating Machines
Science & Mathematics
Data Source
National Museum of American History
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According to John Wolff's Monroe page, this specific machine would have been made earlier than the 1940s. The logo visible in the photo was used in the 1920s and '30s. In the 1940s, a quite different logo was used. The model (LA5-160X) was introduced 1930. L was the based model, very similar to its predecessor, the K line. A means that it's 'automatic' (electric). The 5 refers to the specific sub-model line. The X likely means it's based on the earlier 'Executive' model, though I don't know what aspects might associate it with that. The 160 means that it's got 16 registers. I have the exact same machine, S/N 242584.

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