Thacher's calculating instrument. Comes in large rectangular wooden box (hinged lid, two hooks), with instruction book, "Thacher's Calculating Instrument or Cylindrical Slide-Rule," W.F. Stanley, Pub ., London, 1884. Ends of cylinder have black and brass geometric pattern.
Matériel
"Patented by Edwin Thacher, C. E. Nov. 1st.. 1881. Divided by W. F. Stanley, London, 1882."
