Rare Thacher's Calculating Instrument / Slide Rule by Keuffel & Esser Co, NY

Thacher's Calculating Instrument, by Keuffel & Esser Co. 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.

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. 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.