Open Divided Scale

This 6" boxwood pocket ruler has a white celluloid coating along both long edges on both sides. On one side, the top edge has scales for 1-1/2" and 3" to the foot. The bottom edge has scales for 3/8" and 3/4" to the foot. Between these scales is a scale divided to centimeters, numbered from left to right by twos from 2 to 12, and numbered from right to left by ones from 1 to 6. The middle of this side is marked: U.S. ST'D. It is also marked: P. M. LARSEN.

The top edge of the other side has scales for 1/2" and 1" to the foot. Between these scales is a scale divided to 1/2", numbered from left to right by twos from 2 to 8, and numbered from right to left by ones from 1 to 4. The bottom edge has scales for 1/8" and 1/4" to the foot. Between these scales is a scale divided to 1/8", numbered from left to right by fours from 4 to 44, and numbered from right to left by twos from 0 to 22. The middle of this side is marked: P. M. LARSEN.

Draftsmen used these scales to make construction drawings. Keuffel & Esser sold a similar scale as model 1399P from 1913 to at least 1936. The price in 1913 was $1.35. This object was probably made about the same time as 1981.0933.14, in the 1910s.

William J. Ellenberger (1908–2008) donated this object, which he presumably acquired secondhand from P. M. Larsen. Ellenberger 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, he 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: Catalogue of Keuffel & Esser Co., 34th ed. (New York, 1913), 178; Catalogue of Keuffel & Esser Co., 36th ed. (New York, 1921), 123; Catalogue of Keuffel & Esser Co., 38th ed. (New York, 1936), 212; "The GW Engineering Hall of Fame 2006 Inductees," http://www.weas.gwu.edu/ifaf/hall_of_fame_inductees_2006.php.

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