Keuffel & Esser 4012 Thacher Cylindrical Slide Rule

The brass core of this cylindrical slide rule is covered by paper marked with forty A scales. The core fits in an open rotating frame that holds twenty metal slats; each slat is lined with cloth, covered with paper, and marked with two B and two C scales. Wooden knobs on each end of the core rotate the instrument. The frame is attached to a mahogany base.

The first A scale runs from 100 to 112 and the fortieth runs from 946 to 100 to 105. The first B scale runs from 100 to 112, the last from 946 to 100 to 105. The first C scale runs from 100 to 334, the last from 308 to 305. The paper covering the core is also printed in italics on the right side: Made by Keuffel & Esser Co., New York; Patented by Edwin Thatcher [sic], C.E. Nov. 1st., 1881.

The paper of instructions and rules for operating THACHER'S CALCULATING INSTRUMENT, normally glued to the top front of the base, is coming loose and is torn on this example. A large chip is also missing from the left handle. The top back of the base is stamped: KEUFFEL & ESSER CO. (encircling N.Y.); 4012 (/) 4218; TRADEMARK (below the K&E logo of a lion).

Keuffel & Esser sold versions of the Thacher cylindrical slide rule from about 1883 until about 1950. There were two models, one with a magnifying glass (K&E model 1741 before 1900, K&E model 4013 after) and one without (K&E model 1740 before 1900, K&E model 4012 after). This is a model 4012; the serial number suggests it was manufactured around 1915. The marking on the core also no longer references W. F. Stanley, the English firm that originally manufactured the instrument for sale by K&E. Stanley continued to provide the engine-divided scales after K&E began making the rest of the instrument in 1887. K&E took over printing the scales in the 1910s. Model 4012 sold for $35.00 in 1916, $60.00 in 1922, and $70.00 in 1927.

Compare markings on the core to MA.322730. See also MA.312866 and MA.326628.

References: Wayne E. Feely, "Thacher Cylindrical Slide Rules," The Chronicle of the Early American Industries Association 50 (1997): 125–127; Keuffel & Esser Co., Slide Rules and Calculating Instruments (New York, 1916), 22; Keuffel & Esser Co., Slide Rules and Calculating Instruments (New York, 1922), 21; Keuffel & Esser Co., Slide Rules and Calculating Instruments (New York, 1927), 20.

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