Felsenthal FAO-44 Artillery Protractor

This clear plastic semicircular protractor is divided by twenties and marked by two hundreds from 0 to 3,200 and from 3,200 to 6,400. A pinhole is at the origin point. The interior is labeled: ANGULAR MILS; 8016738. This protractor was item no. FAO-44. Felsenthal Instruments Company manufactured it for the U.S. Army about 1958.
The Felsenthal Instruments Company was the leading supplier of mathematical instruments to the U.S. Army Air Force and the U.S. Navy Bureau of Aeronautics, particularly during World War II (when the firm was known as G. Felsenthal & Sons). After the company ceased operations in approximately 1976, it provided a large sample of its products to the Smithsonian.
See also 1977.1141.01, 1977.1141.02, 1977.1141.03, 1977.1141.05, 1977.1141.08, 1977.1141.09, 1977.1141.11, 1977.1141.12, 1977.1141.18, 1977.1141.19, 1977.1141.20, 1977.1141.21, 1977.1141.22, 1977.1141.23, 1977.1141.24, 1977.1141.30, and 1977.1141.39.
Currently not on view
Object Name
date made
ca 1958
Physical Description
plastic (overall material)
overall: .2 cm x 15.2 cm x 8.3 cm; 3/32 in x 5 31/32 in x 3 9/32 in
place made
United States: Illinois, Chicago
ID Number
accession number
catalog number
Science & Mathematics
See more items in
Medicine and Science: Mathematics
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Ben Wharton Rau and Margery Felsenthal Rau

Visitor Comments

2/6/2013 9:25:23 AM
John Cascio
My father Vincent J. Cascio, worked for this company ( Felsenthal Instruments) for 27 years as a designer and commercial artist. I remember him making the final artwork for this protractor and many other circular slide rulers. Also the memory of the fine people behind the operation of this company. I was very young at the time but I saved many of his aviation slide rule drawings and mathematical notes.
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