Monroe Model L160-X Calculating Machine

This lightweight modified stepped drum full-keyboard non-printing calculating machine is manually operated. It has a gray steel case and gray and white plastic keys, colored to distinguish digits of differing place value. The eight columns of keys each include nine digit keys and one zeroing key. The zeroing key is the opposite color from the rest of the keys in the column. Between the columns of keys, and under the case, are metal rods visible through windows in the case. These serve as decimal markers. To the right of the number keys are two orange buttons, one of which is marked R (for use in repeated addition or subtraction), and an orange clearance key. A crank on the right side rotates clockwise for addition and counterclockwise for subtraction.
In back of the keyboard is the carriage, with 16 result dials and eight revolution register dials. The dials of the revolution register are numbered around the edge from 9 to 0 white and from 1 to 9 in red. A crank for clearing the carriage is on its right side. The carriage shift crank is at the front. Two rubber feet are at the front and two metal standing pieces extend from the back at the bottom, holding the machine at an angle.
This model of the Monroe normally came with a carrying case, but this does not survive.
Compare MA*336523 (1978.0402.01).
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.
Currently not on view
Object Name
calculating machine
date made
Monroe Calculating Machine Company
Physical Description
rubber (overall material)
plastic (overall material)
steel (overall material)
overall: 15 cm x 29.4 cm x 23.7 cm; 5 29/32 in x 11 9/16 in x 9 11/32 in
ID Number
catalog number
maker number
L160-X 628561
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 Albert J. and Delores Cippel, in memory of Sydney F. Toy

Visitor Comments

11/3/2015 9:54:50 PM
Joel Silvey
could this calculator perform multiplication and division? I know more advanced models included the division lever to the upper left of the keyboard area but I'm wondering if the process of division could have been performed manually, especially since the display carriage can be moved to left justified.
12/8/2015 12:34:06 PM
Peggy Kidwell, NMAH
This calculating machine did not perform automatic multiplication or division. The operations were carried out one decimal place at a time, shifting the carriage between subtotals.
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