Keuffel & Esser 1744 Duplex Slide Rule

This ten-inch mahogany rule is coated with white celluloid on the front and back and is held together with straight brass end pieces. Two screws are in one of the end pieces. The indicator is brass in the double chisel style. On one side, the bottom of the base is marked: WM COX. PAT. OCT. 6. 1891. The right side of the top of the base and the slide are both marked: *. On the other side, the bottom of the base is marked: KEUFFEL & ESSER Co. NEW-YORK.

The scales are not labeled. On both sides, the top of the base has an A scale (divided logarithmically from 1 to 10 twice) and the bottom of the base has a D scale (divided logarithmically from 1 to 10 once). One side of the slide has B and C scales. (A B scale is equivalent to an A scale, and a C scale is equivalent to a D scale.) The other side of the slide has BI and CI scales (i.e., B-inverse and C-inverse).

British citizen William Cox received U.S. patent number 460,930 for a duplex "Engineer's Slide-Rule" with these scales on October 6, 1891, and immediately assigned the patent to the Keuffel & Esser Company of New York. This slide rule sold as K&E model 1744 from 1895 to 1900 and as model 4070 from 1901 to 1906. In the 1895 K&E Catalog, which includes the patent drawings in the illustration, the K&E mark is shown near the top of the base instead of near the bottom of the base. The mark is shown near the bottom of the base in the 1897 and 1899 catalogs. The shape of the end pieces was altered in 1901, and a second style of indicator, the glass clam shell, was added as model 4071. By 1909, K&E discontinued model 4070. Thus, this example likely dates to 1896–1900. It would have been partially made by Dennert & Pape in Germany and finished in the United States by K&E, which sold it in a case for $6.50.

K&E donated this slide rule to the Smithsonian in 1961. Compare to model 4071: MA.318475, MA.326613, and 1993.0482.01.

References: Catalogue of Keuffel & Esser Co., 26th ed. (New York, 1895), 186; Catalogue of Keuffel & Esser Co., 28th ed. (New York, 1897), 192; Catalogue of Keuffel & Esser Co., 29th ed. (New York, 1899), 193; Catalogue of Keuffel & Esser Co., 30th ed. (New York, 1900–1901), 296; Catalogue of Keuffel & Esser Co., 32th ed. (New York, 1906), 324; Clark McCoy, "Collection of Pages from K&E Catalogs for the Early 4071 Family of Slide Rules," http://www.mccoys-kecatalogs.com/KEModels/ke4071oldfamily.htm; Wayne E. Feely, "K & E Slide Rules," The Chronicle of the Early American Industries Association 49, no. 5 (June 1996): 50–52; Dieter von Jezierski, Slide Rules: A Journey Through Three Centuries, trans. Rodger Shepherd (Mendham, N.J.: Astragal Press, 2000), 71.

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