Keuffel & Esser 4081-3 Log Log Duplex Decitrig Slide Rule

This ten-inch two-sided slide rule is made from wood coated with white celluloid and held together with metal end pieces. There are L, LL1, DF, D, LL3, and LL2 scales on one side of the base, with CF, CIF, CI, and C scales on the slide. The top of the base is marked in red: KEUFFEL & ESSER CO. N.Y.; PATS. RE.20,984 1,930,852 2,168,056 2,170,144 PAT. PEND.; MADE IN U.S.A. The right end of the slide is marked with the model number: < 4081-3 >. On the other side, there are LL0, LL00, A, D, DI, and K scales on the base and B, T, ST, and S scales on the slide. The left end of the slide and the front left corner of the base are marked with a serial number: 207806. A glass indicator with plastic edges is held together with metal screws. The top edge of the indicator is marked: PATENT 2,086,502. The bottom edge of the indicator is marked: KEUFFEL & ESSER CO. N.Y.

The instrument fits in a cardboard case covered with black leather. Also in the case is a metal straight edge. The case is marked on the top of the flap: LOG LOG DUPLEX (/) TRADE TRIG MARK. The front of the flap is marked: 4080-3 (/) K + E. Stenciled on the case is: T. M. ROBB. Written on the inside of the flap is: THOMAS ROBB (/) SPAIN, AIR CREW.

This combination of scales was used from 1939 to 1947. The serial number on this example is consistent with a date later in this time frame. In 1947, this model sold with the leather case for $19.75. For later examples of model 4081-3, see MA.318482 and MA.334387. On the patents listed on this instrument, see 1992.0437.01 and 1999.0254.01.

Reference: "K + E Slide Rules and Calculating Instruments Price List," July 1, 1947, http://www.mccoys-kecatalogs.com/KECatalogs/1947/1947kecatprice01.htm.; Dieter von Jezierski, Slide Rules: A Journey Through Three Centuries, trans. Rodger Shepherd (Mendham, N.J.: Astragal Press, 2000), 71–75.

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