Perfect condition, very clean, original leather case and strap signed Keuffel & Esser. Long 11.5 inches slide rule, 22 in when extended. Signed Keuffel & Esser 1947, Model 4081-3 Log Duplex Decitrig. This cool tool is actually a mechanical analog computer. It is mainly used for multiplication, division and functions such as exponents, roots, logarithms and trigonometry.