Keuffel & Esser 4088-3 Polyphase Duplex Slide Rule

This ten-inch mahogany duplex linear 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: < 4088-3 >. The bottom of the base is marked in red: PAT. JUNE 5. '00 DEC.22.'08 KEUFFEL & ESSER CO. N.Y. MADE IN U.S.A. The back of the base has K, A, D, and L scales, with B, S, T, and CI scales on the slide. A serial number is at the left end of the slide: 207989. A different serial number is on the front edge: 206079. The indicator is the second generation of Keuffel & Esser's "frameless" glass style, with white plastic edges and metal screws. One edge is marked: KEUFFEL & ESSER CO. The other edge is marked: PATENT 2,086,502.
K&E sold model 4088-3 from 1913 to 1939. From 1913 to 1936, the patent dates were indicated as they are on this instrument. Beginning in 1936, the number of a 1933 patent is shown on drawings of the instrument in K&E catalogs. The B scale was added to the slide in 1922. Both serial numbers are consistent with manufacturing dates in the late 1920s. This style of indicator was introduced in 1936 and patented in 1937. The different serial numbers and the discrepancy in dating between the rule and the indicator suggest that this example consists of components mixed from three slide rules. Compare to MA*318476, MA*321778, and 1981.0933.03. For instructions, see 1981.0933.04 and 1981.0933.06.
References: Adolf W. Keuffel, "Runner for Slide Rules" (U.S. Patent 2,086,502 issued July 6, 1937); Keuffel & Esser Co., Slide Rules and Calculating Instruments (New York, 1922), 8–9; Catalogue of Keuffel & Esser Co., 38th ed. (New York, 1936), 314–315; Ed Chamberlain, "Estimating K&E Slide Rule Dates," 27 December 2000,; Clark McCoy, ed., "Collection of Pages from K&E Catalogs for the 4088 Family of Slide Rules,"
Currently not on view
date made
Keuffel & Esser Co.
place made
United States: New York, New York
Physical Description
mahogany (overall material)
celluloid (laminate material)
glass (cursor material)
metal (part material)
overall: 1 cm x 31 cm x 4.1 cm; 13/32 in x 12 7/32 in x 1 5/8 in
ID Number
accession number
catalog number
Credit Line
Gift of Keuffel & Esser Company
Rule, Calculating
See more items in
Medicine and Science: Mathematics
Science & Mathematics
Slide Rules
Data Source
National Museum of American History, Kenneth E. Behring Center


I have one of these and both serial numbers are the same: 186168. The indicator top edge is marked: "K&E.CO.N.Y.PAT.8.17.15. "The indicator bottom edge just has a black dot.Mine along with the leather holster was probably purchased in 1931 based on the information that came with it.

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