Post 940 Beam Compass

This metal instrument has two I-shaped beams, one 13" long and one 7" long. Needle, pencil, and pen points are moved along a beam by rolling wheels at the top of the trammels. The trammels are each marked with the logo for the Frederick Post Company that was in use from 1944 until 1970 and with the word ERA. A cardboard box covered with black imitation leather holds the objects. The box has two empty 2" slots. The end of the box has a red and white Post label with the model number 940. According to a Post catalog, purchasers could also choose beams as long as 26", 38", 50", 62", 74", 86", and 100".
Reference: Frederick W. Post Company, Dependable Drawing Materials, 19th ed. (Chicago, 1950), 61.
Currently not on view
Object Name
beam compass
date made
Frederick Post Co.
Physical Description
steel (overall material)
cardboard (overall material)
aluminum or aluminum alloy (overall material)
overall: 33.6 cm x 7.5 cm x 2.1 cm; 13 7/32 in x 2 15/16 in x 13/16 in
place made
United States: Illinois, Chicago
ID Number
accession number
catalog number
Science & Mathematics
Drawing Instruments
Dividers and Compasses
See more items in
Medicine and Science: Mathematics
Dividers and Compasses
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Alice W. Smith
Additional Media

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