Keuffel & Esser 4045 Mannheim Simplex Slide Rule

This sixteen-inch one-sided wooden slide rule has scales labeled A and D on the base. There are scales labeled B and C on one side of the slide, with S, L, and T scales on the other side. The A and B scales are divided logarithmically from 1 to 10 twice; the C and D scales are divided logarithmically from 1 to 10 once. The S scale runs from 0 to 80 degrees, and the T scale from 0 to 45 degrees. The L scale is divided logarithmically from 0 to 10. A scale of 40 centimeters is divided to millimeters on the front edge. A scale of 16 inches divided to 1/16-inch is on the other, beveled edge. The scales are all on white celluloid. A table of numerical ratios and equivalences is attached to the back of the rule. A frameless glass indicator was received with the instrument and noted during cataloguing around 1965, but it is no longer present.

The top of the base is marked in red: PAT. JUNE 5, 1900; KEUFFEL & ESSER CO. N.Y.; MADE IN U.S.A. The right end of the slide is marked in red: < 4045 >. The left end of the back of the slide and the left end of the centimeter scale on the base are both marked with a serial number: 46538. The file for the instrument records that the indicator was marked with a patent date of 8.17.15. Compare to MA.322761 and 1987.0634.01.

Keuffel & Esser first advertised the model 4045 Mannheim slide rule in 1906 and stopped selling it between 1936 and 1939. The date on the indicator suggests that this example was made after mid-1915. If the accession file is correct, the rule was given to the Smithsonian by the U.S. Army Signal Corps in 1923. However, the presence of a serial number and the lettering of the A, B, C, and D scales suggest a somewhat later date. (K&E began to assign serial numbers in 1923, and a serial number of 46538 indicates a date around 1925.) Additionally, the accession file records that the slide rule had the Signal Corps type number ML–40. According to the 1920 Storage Catalogue for the Corps, an ML–40 slide rule was a ten-inch polyphase duplex slide rule, graduated on both sides with a frameless glass indicator, specifically "Keuffel & Esser Co.'s No. 4088-3, or equal." Thus, it is possible that this example is not the slide rule received with the 1923 accession. There are no known discrepancies in the files for MA.318480 and MA.321778, the K&E model 4088-3 slide rules acquired by the Smithsonian before 1965, though.

References: Wayne E. Feely, "K & E Slide Rules," The Chronicle of the Early American Industries Association 49, no. 5 (June 1996): 50–52, on 51; Ed Chamberlain, "Estimating K&E Slide Rule Dates," 27 December 2000, http://www.sphere.bc.ca/test/ke/320-k+e_date2.jpg; Signal Corps, Storage Catalogue (Washington, D.C.: Government Printing Office, 1920), 29, 575.

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