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Thacher's Calculating Instrument

The ultimate cylindrical slide rule, invented by Edwin Thacher and patented in 1881. Thacher had the scales divided by W.F. Stanley, in London. However, by 1897, Keuffel & Esser had taken over production. The end of the slide on this example is marked "Patented by Edwin Thatcher, C.E., Nov 1st, 1881". (Stanley misspelled Thacher's name on the original plates, which were, apparently, unchanged during the many years of production by K&E). Also marked on the end of the slide are "Made by Keuffel & Esser Co., New York" and "Divided by W.F. Stanley, London, 1882". The serial number stamped on the wood base of the instrument and on the K&E label inside the box lid is 2675. The instruction booklet accompanying the instrument is dated 1910. The 74 pp book was written and first copywrited by Edwin Thacher in 1884.

The instrument is in very good condition, with no repairs. There is normal aging of the scales including minor chipping. The paper instruction label running along the length of the base has darkened with age, but is intact and legible. The manual is complete and in good condition, except for a tear in the front cover.

the slide rule.
Total knob to knob length is 22 1/2". The scale is 18" long with the 20 segments giving a total of 30 ft.

close up of the scale on the envelope.

the slide and end standard.
The brass support is of the cutout style

the envelope of 20 triangular bars
Note the cloth pads on the inside of each bar which pad the cylinder and provide the correct friction to prevent slipage.
The pads also keep the slide wiped clean.

Markings on the end of the slide
Also marked "Divided by W.F. Stanley, London, 1882" and "Made by Keuffel & Esser Co., New York".

the paper label on the wood base with instructions for use

the Keuffel & Esser box label
K&E model 4012 denotes the instrument without magnifier, model 4013 had the magnifier.

the 1910 manual cover

the manual title page

A brief description of the instrument in Thacher's manual.

Thacher's 1881 patent

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