Keuffel & Esser N4088-5 Polyphase Duplex Slide Rule

This 20-inch mahogany duplex slide rule is coated with white celluloid and held together with L-shaped metal end pieces. The front of the base has DF and D scales, with CF, CIF, and C scales on the slide. The right end of the slide is marked in red: < N4088-5 >. The bottom of the base is marked in red: KEUFFEL & ESSER CO. N.Y.; PAT. JUNE 5. '00 DEC. 22. '08; MADE IN U.S.A. Between the second and third of these marks is scratched: BS37884C.

The back of the base has K, A, D, and L scales, with B, S, T, and CI scales on the slide. The left end of the slide and the front of the rule are marked with a serial number: 235867. A glass indicator has plastic edges held together with metal screws. One edge is marked: K&E.CO.N.Y. (/) PAT.8.17.15. The rule is in a green cardboard box that also contains a paper slip of instructions for adjusting the rule. The back of the slip has a table of equivalents and abbreviations from U.S. Bureau of Standards Circular No. 47. Compare to the tables pasted on the back of slide rules such as 1984.1068.01, MA.321780, and 1987.1084.01. Keuffel & Esser of New York manufactured and sold model N4088-5 from 1936 to 1938 for $22.00.

The physicist Philip Krupen (1915–2001) gave this slide rule to the Smithsonian in 1986. He earned a BS from Brooklyn College in 1935, worked on the development of the proximity fuse during and after World War II, received an MS in physics from The George Washington University, and spent a total of 38 years working for the U.S. government before he retired in 1973.

References: Willie L. E. Keuffel, "Slide-Rule" (U.S. Patent 651,142 issued June 5, 1900); Willie L. E. Keuffel, "Slide-Rule" (U.S. Patent 907,373 issued December 22, 1908); Willie L. E. Keuffel, "Slide-Rule Runner" (U.S. Patent 1,150,771 issued August 17, 1915); Catalogue of Keuffel & Esser Co., 38th ed. (New York, 1936), 314–315; "Price List of K&E Slide Rules," (July 1, 1938), 1; Dieter von Jezierski, Slide Rules: A Journey Through Three Centuries, trans. Rodger Shepherd (Mendham, N.J.: Astragal Press, 2000), 71–75; "Philip Krupen," The Washington Post, February 23, 2001, B07.

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