1540. Original 1944 Keuffel & Esser Polyphase Slide Rule No N4053 Manual Breckenridge. There is discoloration on the covers and on some pages. Doesn’t affect use of the book. Overall in good condition. Always consider offers.

The product is an original 1944 Keuffel & Esser Polyphase Slide Rule No N4053 with a manual. It was manufactured in 1944 and falls under the category of collectibles, science & medicine, and engineering. The slide rule is a tool used for mathematical calculations and was widely used before the advent of electronic calculators. The manual Breckenridge is likely a reference guide for using the slide rule.