Semicircular Protractor Retailed by Post


This semicircular brass protractor is divided by single degrees and marked by tens from 0° to 180° in both the clockwise and counterclockwise directions. The bottom edge is indented so that a pencil or pricker may be placed at the origin point. The protractor bears three marks: POSTS; MADE IN GERMANY; and a fleur-de-lis pointing to the origin. The Frederick W. Post Company, a Chicago mathematical instruments dealer established in 1893, used the type style found on this protractor in the 1920s and 1930s. However, the brass protractor depicted in Post's 1936 catalog is not indented on its lower edge, and it shows an eagle under the maker's mark.

William J. Ellenberger (1908–2008) donated this object. He studied electrical and mechanical engineering at the George Washington University between 1925 and 1934. He then worked for the Potomac Electric Power Company and the National Bureau of Standards. During World War II, Ellenburger served in the U.S. Army Signal Corps. He was a civilian construction management engineer for the army from 1954 to 1968, when he became a private consultant.

References: Frederick W. Post Company, Dependable Drawing Materials, 18th ed. (Chicago, 1936), 195; "The G[eorge] W[ashington] Engineering Hall of Fame 2006 Inductees,"

Date Made: 1920-1940

Maker: Frederick Post Co.

Location: Currently not on view

Subject: MathematicsProtractor


See more items in: Medicine and Science: Mathematics, Science & Mathematics, Protractors


Exhibition Location:

Credit Line: Gift of William J. Ellenberger

Data Source: National Museum of American History

Id Number: 1981.0933.18Accession Number: 1981.0933Catalog Number: 1981.0933.18

Object Name: protractorOther Terms: protractor; Semi-Circular

Physical Description: brass (overall material)Measurements: overall: .1 cm x 9.5 cm x 4.5 cm; 1/32 in x 3 3/4 in x 1 25/32 in


Record Id: nmah_904377

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