Thacher Slide Rule by K&E

Invented by Edwin Thacher in 1878, this unique ribbed cylindrical calculator is 4" diameter and 18" long, providing logarithmic scales of 30 feet length and four to five digit accuracy.
Patented in the USA in 1881, it was first made by W. F. Stanley in England, but production was moved to New York around 1900 after Keuffel & Esser Co. acquired the manufacturing rights.
Most of Thacher production was two basic models, 4012 and 4013, being the same except the 4013 has a magnifier that travels on a rod in front of the scales and is much scarcer than the 4012.
With fewer than 7,000 Thachers made over a 70 year period, they are highly prized by slide rule collectors.