DescriptionLog Log Duplex Decitrig model 4081-3 (as marked; actually 4081-3S), 10" slide rule, made by Keuffel & Esser Co., New York and Hoboken, copyright 1947, probably sold ca. 1955-1960. Mahogany with laminated white celluloid plastic ruled in red and black; bottom and top edge have inset white plastic (top with markings recorded below); metal end pieces; 12-1/2" overall length x 1-5/8" high (2" with indicator) x 3/8" thick (includes thickness of metal end brackets. Metal framed glass indicator (cursor) with adjustable slide. Serial number 957861. With: sewn black leather case (sheath) with K&E logo blind stamped on flap. Bottom edge has model and maker's marks including five patent numbers. From left: Pats. Pend.l Made in U.S.A.; 4081-3; Log Log Duplex Decitrig; Copyright 1947 by; Keuffel & Esser Co.; Pats. 2,500,460 2,168,056 2,170,144 2,285,722 2,422,649 [which was issued June 17, 1947.] The change of the 'ST' scale (in list below) to 'SRT' scale apparently happened circa 1955 Description on page 237 of K&E 41st edition catalog, 1949 (which also has picture of it): N4081-3. LOG LOG DUPLEX DECITRIG Slide Rule, like No. N4080-3, but with Trigonometrical Scales divided to represent degrees and decimals of a degree. N4081-3S. Same as No. N4081-3, but in sewed Leather Case. List of scales as found on the same page. On one face are the following scales: LL02: a Log Log scale of range 0.905 (e-0.1) to 0.368 (e-') LL03: a Log Log scale of range 0.368 (e-') to 0.00005 (e-10) DF: a full length B scale folded. This arrangement admits of the handling of factors which, in rules without these scales, would frequently require the slide to be reset. Since the constant 'w is in alignment with the indices of the C and B scales, can he taken as a factor or divisor in any formula without an additional setting. CF: a full length C scale, folded like the DF scale. CIF: a full length inverted folded scale, giving reciprocals of numbers on the CF scale. The inverted scale, in connection with the direct scales, admits of handling three factors with one setting of the slide, or four factors if [pi symbol] is included. CI: a full length C scale inverted. C: a single logarithmic scale. D: a single logarithmic scale like C. LL3: a Log Log scale of range 2.718 (e') to 22000 (e10). LL2: a Log Log scale of range 1.105 (et.1) to 2.718 (e'). On the reverse face are the following scales: LL01: a Log Log scale of range 0.99 (e-°.°') to 0.905 (e-°.1). K: a three unit logarithmic scale, giving directly cubes and cube roots. A: a two unit logarithmic scale giving directly squares and square roots. B: a two unit logarithmic scale likd A. T: a full length scale of Tangents and Cotangents, double numbered; of range 5°43' or 5.71° to 84°17' or 84.29°. ST [marked SRT on this one]: a full length scale of Sines and Tangents, of range 0°34' or 0.57° to 5°44' or 5.74°. S: a full length scale of Sines and Cosines, double numbered of range 5°44' or 5.74° to 90° for Sines, and 0° to 84°lG' or 84.26° for Cosines. D: a single logarithmic scale. L: a scale of equal parts (decimal exponents of 10). LL1: a Log Log scale of range 1.01 (e°.°1) to 1.105 (e 0.1).