Keuffel & Esser 4070-3 Polyphase Duplex Trig Slide Rule

This ten-inch mahogany duplex slide rule is coated with white celluloid and held together with metal endpieces that are significantly corroded. On one side, the base has DF, D, and L scales, with CF, CIF, CI, and C scales on the slide. The top of the base is marked in faded red: KEUFFEL & ESSER CO.; PATS. 2,500,460 2,168,056 2,170,144 PAT. PEND.; MADE IN U.S.A. The right end of the slide is marked in red: © (/) K + E; < 4070-3 >. On the other side, the base has K, A, D, and DI scales, with B, T, ST, and S scales on the slide. The left end of the slide has a serial number: 952594. The top and bottom of the base are both marked at the left end: 594. The indicator is glass with plastic edges; it is so corroded that it has fallen apart and is no longer on the rule.

There is a green leather case with white inlays on the holder for the flap. The flap is marked: K + E. Inside the flap is written in ink: Jeffery (/) Smith (/) P 68. An orange chamois case holds a magnifier with two lenses and a metal frame. On one side, the frame is marked: K + E. On the other side, the frame is marked: PAT. NO. 2556806. A green cardboard box, missing one end, holds the rule, its case, the magnifier, and its case.

For information on the patents on the rule, see 1993.0482.01 and 2007.0181.01. Paul E. Gaire of Manasquan, N.J., received a patent for the magnifier in 1951, replacing his earlier attempt at a magnifier, which could only be used on one side of a slide rule at a time. This double magnifier was first advertised in Keuffel & Esser's 1954 catalog and first pictured in the 1962 catalog; it sold for $5.50. K&E sold this version of the model 4070-3 slide rule from 1952 to 1962, at a price of $20.50.

References: Paul E. Gaire, "Magnifying Runner for Slide Rules" (U.S. Patent 2,556,806 issued June 12, 1951); K + E Catalog, 42nd ed. (New York: Keuffel & Esser Co., 1954), 276–277; Keuffel & Esser Co., Slide Rules, Catalog 8 (Hoboken, N.J., 1962), 29–30; Clark McCoy, ed., "K&E Catalogs and Price Lists for Slide Rules," http://www.mccoys-kecatalogs.com/KEmain.htm.

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