Koch & Co. Protractor

This device for measuring angles bears some resemblance to a combination of a sector and dividers. Two steel arms are screwed together so that one arm may be squeezed and the tops of the arms may pinch an object. The stationary arm is split so that the tension on the arms may be adjusted at the screw. The stationary arm is fastened to a brass piece that is divided by single degrees and marked by tens from 0° to 100°. When the other arm is squeezed, it points to a measurement on the brass piece.
An owner's signature on the back of the brass piece appears to read, in script, "bgulp." The letters may be Cyrillic or German. A maker's mark is stamped on the back of the stationary arm: KOCH & Co. The firm to which this maker's mark refers is not known. The Department of Entomology in the National Museum of Natural History acquired this object in the late 19th century for use in research. The object is rusted and tarnished.
Currently not on view
Object Name
date made
before 1900
Koch & Co.
Physical Description
brass (overall material)
steel (overall material)
overall: .4 cm x 15 cm x 9 cm; 5/32 in x 5 29/32 in x 3 17/32 in
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
Transfer from National Museum of Natural History
Additional Media

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