Monroe Model E Calculating Machine


This full-keyboard manually operated non-printing modified stepped drum calculating machine has a steel frame painted black. The eight columns of round plastic keys are colored black or white according to the place value of the digit represented. The key stems are banked, standing up further toward the back of the machine. A row of red clearance keys is at the front of the keyboard; a red key for clearing the entire keyboard is on the right side. Between rows of keys are metal strips, painted black on one side and white on the other, that turn to serve as decimal markers. Ther two silver-colored knobs have arrows on them. One on the right is used for automatic keyboard release in continuous addition. One on the left is the register key for the item counter.

A carriage behind the keyboard has 16 black total register dials and eight white revolution register dials. The revolution register has black digits for addition and red ones for subtraction. A metal operating handle with a wooden knob is on the right side. Another handle on the right side of the carriage zeros the total register or the revolution register, depending on the direction in which it is turned. A knob on the right side of the carriage is used to lift it. A crank at the front of the machine rotates to move the carriage. The machine has four rubber feet.

A partly obliterated mark on the front reads: MONROE (/) REGISTERED TRADEMARK (/) Calculating Machine Company (/) New York, U.S.A. A mark in the middle of the back of machine reads: E5681.

This particular machine came to the Smithsonian from Feldman’s Department Store in Baltimore, Maryland, when the then fifty-year old family business was liquidated in 1974.

According to McCarthy, Monroe began manufacturing the Model E in 1916, using serial numbers beginning at 4,000. Monroe received a registered trademark for its machines in 1920, and began marking objects to that effect. In 1921 it replaced its earlier models with the model K. Hence the date assigned.


E. Martin, The Calculating Machines (Die Rechenmaschinen), trans. P.A. Kidwell and M.R. Williams, Cambridge: MIT Press, 1992, p. 265.

J. H. McCarthy, The American Digest of Business Machines, Chicago: American Exchange Service, 1924, pp. pp, 80–81, 551.

U.S. Patent and Trademark Office, Trademark Registration 129029, Serial #71117235.

Accession file.

Date Made: 1916

Maker: Monroe Calculating Machine Company

Location: Currently not on view

Place Made: United States: New York, New York City

Subject: Mathematics


See more items in: Medicine and Science: Mathematics, Calculating Machines, Science & Mathematics


Exhibition Location:

Credit Line: Gift of Feldman’s Inc.

Data Source: National Museum of American History

Id Number: MA.334403Catalog Number: 334403Maker Number: E5681Accession Number: 316382

Object Name: calculating machine

Physical Description: steel (overall material)wood (overall material)aluminum (overall material)plastic (overall material)rubber (overall material)Measurements: overall: 16 cm x 43.5 cm x 32 cm; 6 5/16 in x 17 1/8 in x 12 19/32 in


Record Id: nmah_690554

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