Lawrence Engineering Service 10-B Mannheim Simplex Slide Rule

This inexpensive 9-1/2 inch one-sided wooden slide rule is painted white on the front face. A, D, and K scales are on the base, and B, CI, and C scales are on one side of the slide. A plastic indicator is in a metal frame. The top of the base is marked: MADE IN U.S.A. It is also marked LAWRENCE ENGINEERING SERVICE, PERU, INDIANA and PAT. PEND. The right end of the slide is marked: 10-B. Tables for equivalents and conversions appear on the back of the instrument, which is in a cardboard box covered with black synthetic leather.

George Lee Lawrence (1901–1976) established a firm in Chicago to make slide rules for photography. In 1935 he moved to Wabash, Ind., renamed the company Lawrence Engineering Service, and began to manufacture general purpose slide rules. In 1938 he relocated once more to Peru, Ind., probably to enlarge the factory. Lawrence's second wife, Vivian Breyer, received the company in their 1947 divorce. Its name was changed to Engineering Instruments, Inc., and the company remained in business until its building burned down in 1967. Thus, this rule dates between 1938 and 1947. The model 10-B sold for 25 cents during this period. There is no record that Lawrence ever received a patent for any aspect of his design or manufacturing process. According to the donor, this rule belonged to her father, George L. Sterns. Compare to 1980.0097.02.

References: Bruce Babcock, "Lawrence Engineering Service — A Tale from an American Small Town," Journal of the Oughtred Society 5, no. 2 (1996): 55–61; David G. Rance, "The Unique Lawrence," Proceedings of the 17th International Meeting of Slide Rule Collectors (September 2011), 87–107, http://www.sliderules.nl/index.php?p=papers; Peter M. Hopp, Slide Rules: Their History, Models, and Makers (Mendham, N.J.: Astragal Press, 1999), 195–196; accession file.

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