Keuffel & Esser 4071 Duplex Slide Rule

This ten-inch duplex mahogany slide rule is coated with white celluloid on the front and back; the edges are bare. Unlike earlier slide rules from the Keuffel & Esser Company, such as MA.318477, the end pieces are silver-colored metal (not brass) and the indented edges of the end pieces face in instead of out. The indicator is glass in a brass frame, which was called the "clam shell" style.

The scales are labeled. On both sides, the top of the base has an A scale and the bottom of the base has a D scale. The slide has B and C scales on one side and BI and CI scales on the other side. On one side, the bottom of the base is marked: KEUFFEL & ESSER Co.N.Y. It is also marked there: B.S.5470. On the other side, the bottom of the base is marked in red: PAT. OCT. 6. 1891. The bottom edge of the indicator is engraved: KEUFFEL & ESSER CO (/) NEW–YORK.

The instrument fits in a cardboard box covered with black morocco leather. The large part of the box is embossed: KEUFFEL & ESSER Co. (/) DUPLEX (/) SLIDE RULE. The U.S. National Bureau of Standards (now the National Institute of Standards and Technology) transferred this instrument to the Smithsonian in 1965 as excess property.

K&E sold this instrument as model 4071 from 1901 to 1917. By this time, K&E was manufacturing slide rules from start to finish at its factory in Hoboken, N.J. In 1913, the shape of the end pieces was changed to an "L," as with MA.318475. That instrument also has patent dates of 1900 and 1908 on it, suggesting that this slide rule dates from 1908 or earlier. The 1909 catalog describes the 1908 patent as "pending." Model 4071 initially sold for $8.00 and was reduced to $7.00 in 1906 and to $5.00 in 1909.

References: William Cox, "Engineer's Slide-Rule" (U.S. Patent 460,930 issued October 6, 1891); 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; Catalogue of Keuffel & Esser Co., 30th ed. (New York, 1900–1901), 296; Catalogue of Keuffel & Esser Co., 31st ed. (New York, 1903), 306; Catalogue of Keuffel & Esser Co., 32th ed. (New York, 1906), 325; Catalogue of Keuffel & Esser Co., 33rd ed. (New York, 1909), 312; Catalogue of Keuffel & Esser Co., 34th ed. (New York, 1913), 303.

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