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Since 1867 Keuffler & Esser has had a hand in producing & designing superior products, but it wasn't until 1891 that they extended their expertise to the manufacturing of slide rules. Eventually K&E cornered the market for professional engineer-grade rules; quality which can be seen in this 1947 example of the N4080-3 Log Log Duplex Trig Slide Rule. Made in the USA from hardwood mahogany surrounded by white cellulose on all sides, this 10" double-sided (duplex) slide rule permitted scales to be placed on either side. An internal sliding middle section and a patented movable 'glass-enclosed hairline' on front-and-back made it possible to read/use the scales together.
Enough about the history of K&E, let's talk about this slide rule:
• Appears to be hardly used, or at least gently used. No scratches, bumps or dents anywhere - near new condition.
• Comes with its original K&E leather case.
• RARE outer original green outer box is included, with product label "K&E N4080-3".
• Box measures approx. 13" x 3" x 1.5"
• Contains small booklet, "How to Take Care of Your K&E Slide Rule".
• Markings on edge of slide rule: Serial (511113) | Pats.Pend. | Made in U.S.A. | N4080-3 | Log Log Duplex Trig | Copyright 1947 by Keuffel & Esser Co. | Pats. 1,930,852 2,168,056 2,170,144 2,285,722 2,422,649
Condition Notes: Green box shows some wear appropriate to age, especially to corners. Written inside box is the owner's name, which is also written inside of leather case.