Open Triangle

Open Triangle

Usage conditions apply
This 7-7/8" 45°-45°-90° xylonite triangle had a small triangular cutout in its interior. The edges of the opening had bevels to make it easier to pick up the object while making engineering drawing. The triangle was marked: 8. Keuffel & Esser and Dietzgen sold similar triangles for 75¢ in the first decade of the 20th century. Compare to MA.304722.08.
According to the donor, Alfred John Betcher (1887–1971) used this triangle while he was a student at the University of Minnesota in 1906. He transferred to West Point in 1907 and graduated in 1911. He served in the Philippines, Texas, New York, France, Vermont, and Kentucky. He retired in 1939 at the rank of lieutenant colonel. In 1940 he was elected mayor of Canajoharie, N.Y.
Early plastics were chemically unstable. Although this object was received in 1982 in good condition, over time the xylonite became crazed and, while it was in storage, the triangle spontaneously broke into several pieces. It could not be repaired and so was destroyed in 2000. Hence it is unavailable for study or loan.
References: Catalog of Eugene Dietzgen Co., 7th ed. (Chicago, 1904), 196; Catalogue of Keuffel & Esser Co., 33rd ed. (New York, 1909), 208; George W. Cullum, Biographical Register of the Officers and Graduates of the U.S. Military Academy, supp. vol. VI-B, ed. Wirt Robinson (Saginaw, Mich., 1920), 1532; accession file.
Object Name
date made
ca 1906
Physical Description
plastic (xylonite) (overall material)
overall: 20 cm x 20 cm; 7 7/8 in x 7 7/8 in
ID Number
catalog number
accession number
Credit Line
Gift of John A. Betcher
Drawing Instruments
Drafting, Engineering
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Data Source
National Museum of American History
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