Ensign Model 90 Calculating Machine

This full-keyboard direct multiplication non-printing electric calculating machine has an iron and steel case painted black, The nine columns of plastic black and white keys are colored according to the place values represented. Complementary digits are indicated on the keys. Keys for odd digits are concave, and those for even ones are flat. The keyboard is covered with green felt.
Right of the number keys is an addition bar. Considerably to the right of this is a key to be depressed in division and ten digit keys used to enter digits directly in multiplication. To the left of the keyboard is a key marked “C” that, when depressed, locks the keyboard. A row of seven number dials serves as a revolution counter. These dials are covered with glass.
On the left side is a handle for clearing the revolution counter and result register. Behind the keyboard and revolution counter, inside the machine, in a row of 16 number dials recording the result. These dials are also covered with glass. They are deep within the machine, and difficult to read. The result register may be divided to record two results simultaneously. The base of the case is open, with a cloth cover inside it. This example has no motor.
A mark on the front of the machine reads: The Ensign. A mark on the right side reads: ENSIGN (/) MANUFACTURING CO. (/) BOSTON, U.S.A. (/) PATENTED (/) NOV. 1, 1904. - JAN. 2, 1906. (/) JULY 9, 1907. - FEB. 18, 1908 (/) JUNE 2, 1908. (/) OTHER PATENTS PENDING.
The Ensign was an early example of an electrically operated calculating machine. The Ensign Manufacturing Company of Waltham, Massachusetts is listed in Thomas’ Register for 1909. The dates on the machine refer to dates of patents of Emory S. Ensign, who was president of the company. The Ensign Manufacturing Company of Boston, Massachusetts, is listed in Thomas’ Register for 1912, 1914, 1915, 1916, and 1917. It was not listed in 1918. By this time, Ensign seems to have moved to Queens, New York. The machine was manufactured until about 1925.
This example is from the collection of Felt & Tarrant Manufacturing Company.
E. Martin, The Calculating Machines (Die Rechenmaschinen), trans. P. A. Kidwell and M. R. Williams, Cambridge: MIT Press, 1992, pp. 189–191.
Thomas’ Register of American Manufacturers, New York: Thomas Publishing Company.
J. H. McCarthy, The American Digest of Business Machines, Chicago: American Exchange Service, 1924, p. 23.
E. S. Ensign, "Calculating-Machine," U. S. Patent 773,632, November 1, 1904.
E.S. Ensign, "Calculating-Machine," U.S. Patent 859,552, July 9, 1907.
E. S. Ensign, "Calculating Machine, U.S. Patent 879,449, February 18, 1908.
E.S. Ensign, "Calculating-Machine," U.S. Patent 889,668, June 2, 1908).
E. S. Ensign, "Drive for Calculating-Machines," U.S. Patent 1,331,561, February 24,1920. Ensign applied for this patent in 1916.
Currently not on view
Object Name
calculating machine
date made
ca 1915
Ensign Manufacturing Company
Physical Description
plastic (overall material)
glass (overall material)
steel (overall material)
felt (overall material)
overall: 16.5 cm x 50 cm x 25 cm; 6 1/2 in x 19 11/16 in x 9 27/32 in
place made
United States: Massachusetts, Boston
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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