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1911 THACHER'S CALCULATING INSTRUMENT No. 4012 by KEUFFEL & ESSER 

American, ca 1911, signed on the inner cylinder "Made by Keuffel & Esser Co. New York" and serial numbered 2741. The calculator consists of a cylinder 4" in diameter and 18" long, which revolves in an open framework composed of 20 angular bars held between two metal rings. The cylinder bears a scale corresponding to the scale of the slide rule, which is duplicated on the exposed sides of the bars. Results can be obtained to fourth, and usually to fifth place accuracies. 

This Thacher is in unusually good overall condition, showing very little wear and no discolouration or spotting to the paper scales on the rails, the inner cylinder, or the base - a hairline separation in the paper on the inner cylinder occurred during manufacture, but the separation is completely sealed by the original clear finish applied to the paper. The original 23 3/4" long x 6 3/4"" wide x 6 1/4" high dovetailed mahogany box is in good overall condition, showing wear to the exterior.



!!! References

* [[http://www.mccoys-kecatalogs.com/KEManuals/4012_1892/4012_1892.htm|Manual for the 4012 K&E Thacher Calculating Instrument]]