Monroe Model 8N-213 Calculating Machine

This fully automatic electric non-printing modified stepped drum calculating machine has a gray and black steel frame, and ten columns of gray and white oblong plastic keys. At the bottom of each column is a key for clearing it. Between the columns of keys and under the keyboard are metal rods which turn to serve as decimal markers. They are painted white on one side and the same black as the case on the other.
To the right of the number keys are subtraction and addition bars, two carriage shift keys, and a green enter multiplier key. Below these are three levers, one to set repeated entries, one for multiplication, and one for non-entry. Below these are three red keys relating to entering the dividend, a gray keyboard clearance key, and a lock lever. Beneath the number keys are five keys relating to multiplication and division. A DIVD ALIGN key is left of these.
The carriage in back of the keyboard has ten dials to show a number set up for multiplication, 21 dials to show the result, and a row containing ten white dials and then 11 black dials. Sliding decimal markers are provided. The dials showing numbers set up for multiplication can be set at any of five positions. A metal piece slides over the windows for these dials to indicate the decimal point. A gray electrical cord attaches to the back. The gray cover is separate.
A mark on the carriage reads: MONROE. The same mark is on the back of the machine, with the Monroe logo trademarked in 1956. A mark on both right and left sides reads: MONROmatic. A paper sticker glued to the bottom of the machine reads: MONROE (/) CALCULATING MACHINE (/) COMPANY, INC. (/) ORANGE, N.J. U.S.A.. It also is marked with patent numbers that range from 2,250,403 to 2,732,129. The second patent date is from 1953. A metal tag attached to the bottom of the machine reads: MODEL 8N-213 (/) SERIAL B973812B. There is no mention of Litton Industries, which acquired Monroe Calculating Machine Company in 1958.
According to the accession file, the machine was purchased by the University of Pittsburgh 14 September 1960, at a cost of $880, for use in parapsychological research.
Compare to MA*335425 and 1984.3046.01.
Accession file.
Currently not on view
Object Name
calculating machine
date made
Monroe Calculating Machine Company, Inc.
Physical Description
rubber (overall material)
plastic (overall material)
steel (overall material)
overall: 20.5 cm x 37 cm x 34.2 cm; 8 1/16 in x 14 9/16 in x 13 15/32 in
place made
United States: New Jersey, Orange
ID Number
catalog number
maker number
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 University of Pittsburgh
Additional Media

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