Vintage Keuffel & Esser slide rule complete with its original leather case marked “ARMY 406.” This mid‑century engineering instrument features multiple precision calculation scales and a smooth‑gliding cursor framed in metal. The slide rule shows light age wear consistent with use, while the case retains its original stitching and flap closure.
The leather case displays authentic patina and markings, adding historical character and possible military provenance. The slide rule itself remains fully legible and functional, ideal for collectors, engineers, or STEM enthusiasts who appreciate historical drafting tools.
Slide rule: Very good vintage condition; clear scales and smooth cursor movement.
Case: Surface wear, scuffs, and markings consistent with age and prior field use.
No cracks or structural damage noted.
Brand: Keuffel & Esser Co.
Era: Circa 1940s–1950s
Material: Ivory‑tone composite with metal cursor and leather case
Markings: “ARMY 406” handwritten on case