Mathematical Treasure: Trigonometer for Use with Artillery
Barnaby C. Keeney’s trigonometer, ca 1942, Smithsonian Institution negative number DOR2013-17462
Interconnections between the angles and the lengths of the sides of triangles have long interested not only mathematicians and astronomers, but also those surveying land and aiming guns. Trigonometric scales were incorporated into instruments such as quadrants, sectors, and slide rules. During World War II, special-purpose instruments like this one were provided to those training to be antiaircraft officers in the U.S. Army. Barnaby Conrad Keeney (1914–1980), who used this instrument during his training, would go on to complete a doctorate in history and then serve as president of Brown University. He apparently gave his trigonometer to the Mathematics Department at Brown, which in time presented it to the Smithsonian.
Several instruments utilizing plane trigonometry, including this one, are shown at: https://americanhistory.si.edu/collections/object-groups/trigonometry-in-the-plane.