on the corner of leather case, there are small mark as you can see in last picture Please make sure you check all pictures for condition discontinued item from early-mid 20th century
Vintage K&E Keuffel & Esser Polyphase Slide Rule, Model N4053-3, made in the USA with patented date marked June 5, 1900. Features a mahogany wood body with celluloid laminate and crisp, legible scales. Comes with original leather case (shows wear on back), embossed with "K&E Polyphase Slide Rule." Includes reference tables on reverse. Excellent condition overall with no major damage or cracks . A classic engineering tool for collectors, math enthusiasts, or vintage décor display.