Kern Semicircular Protractor

This German silver semicircular protractor bears the distinctive italic engraved numbers of Kern & Co. of Aarau, Switzerland. It is graduated by quarter-degrees and marked by tens from 10 to 170 both from left to right and from right to left. There are no other marks. The lower edge of the protractor is beveled, with a groove at the origin point.
Ruth E. Crownfield, the widow of Albert C. Crownfield Jr., a mechanical engineer from Mohawk, N.Y., donated this protractor in 1978. The instrument is quite tarnished and scratched, suggesting Crownfield used it frequently. Similar protractors cost $3.50 in the first decade of the 20th century and $4.50 in 1936.
See also ID numbers MA*247966 and 1977.0460.02.
References: “(Product No.) 1248,” Catalogue of Keuffel & Esser Co. (New York, 1909), 172; Catalogue of Keuffel & Esser Co. (New York, 1936), 201.
Currently not on view
Object Name
date made
early 20th century
Kern & Co.
Physical Description
german silver (overall material)
overall: .2 cm x 15.6 cm x 7.9 cm; 3/32 in x 6 5/32 in x 3 1/8 in
place made
Schweiz: Aargau, Aarau
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 Ruth E. Crownfield
Additional Media

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