This quality made Keuffel & Esser Co. slide rule looks to be much older than most we see. The white surface appears to be bone or some other natural or faux material – we’re unsure. Slide Rule is in excellent shape with only a tiny piece of white material missing on one end – see last photo. Hardly noticeable. The condition overall is excellent thanks to its surviving original box, which itself is in relatively good shape for its vintage. The slide works smoothly and is marked with the serial number: <4041>. The total length is 10.25 inches closed and 21 inches extended. The box bears the marking “”N.U. / W.B. GOFF”. A great piece for collection, display, or use.