Felsenthal FAE-18 Artillery Protractor

This clear plastic semicircular protractor is divided to ten mils and marked by hundreds from 100 to 3,100 and from 3,300 to 6,300. The bottom edge is divided by quarter-yards and marked by ones from 0 to 26. There is a vernier to the left of the divisions, and the scale is given as 1:10,000. Inside the divisions is a second ruler, divided by two yards and marked by twos from -2 to 52. The scale is given as 1:20,000.
A rectangular slot inside these rulers is divided by half-inches and marked by ones from 0 to 7. A vernier is to the left of this ruler. The upper interior of the protractor contains two scales forming a right-angled point. There are ten divisions between each unit on the scales. The outer markings are by ones from 0 to 10 and are labeled: YARDS 1:20,000. The inner markings are by twos from 2 to 20; they are labeled: YARDS 1:40,000.
The interior of the protractor also bears several marks: U.S. (/) W = (R X M)/1000; M = (W X 1000)/R. The maker's mark is toward the right side: FSN 6675-641-5711 (/) G. FELSENTHAL & SONS, INC. (/) CHICAGO 18, ILL. (/) FAE-18.
Donor Ben Rau identified the object as a machine gun protractor and dated it to 1945. It was manufactured for the U.S. Army.
See also 1977.1141.01, 1977.1141.02, 1977.1141.03, 1977.1141.05, 1977.1141.08, 1977.1141.09, 1977.1141.10, 1977.1141.11, 1977.1141.12, 1977.1141.18, 1977.1141.19, 1977.1141.20, 1977.1141.21, 1977.1141.22, 1977.1141.23, 1977.1141.30, and 1977.1141.39.
Currently not on view
Object Name
date attributed by donor
date made
ca 1945
G. Felsenthal & Sons, Inc.
Physical Description
plastic (overall material)
overall: .1 cm x 25.3 cm x 14 cm; 1/32 in x 9 31/32 in x 5 1/2 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

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