Baldwin Calculating Engine

This is the U.S. Patent Office model for a printing pinwheel calculating machine patented by Frank S. Baldwin of St. Louis, Mo., in 1875. The machine has a brass base, two open brass pieces on each side that form a frame, and a brass, steel, and wooden mechanism. A cylindrical drum mounted horizontally on the frame is 11.5 cm. (4-1/2”) in diameter and 5 cm. (2”) in height.
Both ends of this drum are perforated with six round holes. The drum slides along the shaft into a series of position and may be fixed in place by a small lever. Along the surface of the drum are three slots in which levers slide. The levers may be set at any digit from 0 to 9. Moving a lever from 0 to a given number moves a steel arc that pushes the corresponding number of pins above the surface of the cylinder opposite the lever. Rotating the large cylinder rotates a series of intermediate wheels in proportion to the number of raised pins.
These wheels are linked to a set of seven cogwheels, each having ten teeth. On the outer edge of each tooth is a number in type, the numbers ranging from 0 to 9. These cogwheels are linked to a second set of three larger cogwheels that also have digits in type. These wheels may be intended to indicate the multiplier. The front of the two sets of type-wheels has a brass cover that contains a manually operated printing mechanism. The machine has no paper or ribbon
The machine is marked on the large cylinder next to the slots for the three levers: F.P. Baldwin (/) St. Louis, Mo.
Baldwin applied for his patent September 8, 1873. A few examples were manufactured and sold by the Reliance Machine Works of Philadelphia.
Compare to a production model of the machine, MA*310229.
U.S. Patent 159244, February 2, 1875.
“Baldwin’s Arithmometer,” Philadelphia, Reliance Machine Works, about 1875.
P. A. Kidwell, “The Adding Machine Fraternity at St. Louis: Creating a Center of Invention, 1880–1920,” IEEE Annals of the History of Computing, 22 #2 (April–June 2000), pp. 4–21.
Currently not on view
Object Name
calculating machine
date made
date patented
1875 02 02
Baldwin, Frank S.
Baldwin, Frank S.
Physical Description
steel (overall material)
brass (overall material)
wood (overall material)
overall: 13.5 cm x 13.5 cm x 23 cm; 5 5/16 in x 5 5/16 in x 9 1/16 in
place made
United States: Missouri, St. Louis
place patented
United States: Missouri, St. Louis
ID Number
catalog 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

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