Thacher's Calculating Instrument, by Keuffel & Esser Co., New York, Model no. 4012, serial no. 4010, patented by Edwin Thacher 1881, with outer paper-covered scales on revolving brass rings, and 19-inch sliding inner cylinder, on mahogany base and end handles with paper instruction label, in mahogany case. Manufacturer’s tag appears on inside of case cover, as well as stamped on the mahogany base.
The Thacher calculator has a near unique sliding drum design whose scales total over 30' long if laid out in a line. Edwin Thacher first patented the idea for this slide rule / calculator in 1881 in England. The idea was an immediate success with the scientific and engineering communities. K & E bought they rights to sell and manufacture the popular rule. Stanley initially produced them in England for K & E. and production was moved to the states near the turn of the century. The Thatcher calculator was first offered by K & E in their 1887 catalog as the 1740-N. In 1890 they dropped the N. In 1899 they changed the calculators # to 4012 or 4013. The 4013 being the upgraded model w/ a built in magnifier. There were approx. 7000 total units made. The inventors name is Thacher, but it was misspelled Thatcher on almost all versions of the calculator that K & E offered, hence the use of two different spellings of Thatcher / Thacher.
This calculating instrument is in fair condition, with paper losses on the metal scales, rust, corrosion, and other imperfections and wear from age and use. Dimensions: Instrument: 5 ¾” h x 22 ½” w x 5 ½” d; Case: 6 ¼” h x 23 ¾” w x 6 ½” d.
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