Vintage Keuffel & Essex Co., NY Slide Rule

Very rare Keuffel & Esser duplex slide rule. It is model 4080-3 which has Trig scales. It has the experimental “clamshell” cursor that was used for a very short period before the column cursor. This rule is in excellent condition. I have not cleaned it; it is as found. All moving parts slide as they should. There is serial number 245566 stamped into the end of the three wooden rules. There are patents annotated in several places. Original leather case and box are included; see photos.