Keuffel & Esser 4092 Log Log Duplex Slide Rule

This ten-inch mahogany duplex slide rule is faced with yellowed white celluloid and held together with corroded L-shaped end pieces. On one side, the base has A and D scales, with B, S, and C scales on the slide. The left end of the slide is marked in red: < 4092 >. The bottom of the base is marked in red: KEUFFEL & ESSER CO. N.Y.; PAT. JUNE 5. '00 DEC. 22. '08. On the other side, the base has LL1, LL2, LL3, D, and L scales, with C, T, and CI scales on the base. The indicator is frameless glass with plastic edges fastened with screws. One edge is marked: K&E.CO.N.Y. (/) PAT.8.17.15.

Keuffel & Esser of New York offered model 4092 from about 1909 to 1921. The frameless glass indicator was introduced in 1915. The rule sold for $8.00 from 1909 through 1915 and for $12.50 in 1921. This example fits in a cardboard case covered with black leather and marked: KEUFFEL & ESSER Co. (/) LOG. LOG. (/) SLIDE RULE. For instructions, see 1981.0993.02. Later examples of K&E Log Log slide rules in the collections include 1984.1068.02, MA.318479, 1990.0687.01, 1986.0790.03, and 1987.0085.01.

The donor, William J. Ellenberger (1908–2008), 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., 33rd ed. (New York, 1909), 312; Catalogue of Keuffel & Esser Co., 35th ed. (New York, 1915), 304; Catalogue of Keuffel & Esser Co., 36th ed. (New York, 1921), 240; "The GW Engineering Hall of Fame 2006 Inductees," http://www.weas.gwu.edu/ifaf/hall_of_fame_inductees_2006.php.

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