Full Details

Name and Model Number	Keuffel & Esser 4071-T
Country of Origin	USA
Date of Manufacture	Cox duplex patent date of October 6, 1891
Front Scales	A B Tm CI D
Back Scales	A B D C D
Scale Length	25 cm (10 inches)
Type of Rule	Slide Rule
Construction	Celluloid on Mahogany – fixed end frames - open out.
Area of Use	Generic
Comment	Unusual clam shell cursor –log scale on edge - This example is unmarked as to model. Old Cox patent, K&E duplex
Rarity	RRR
Donor	Collection of Clay Castleberry
Match Number	296
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In conjunction with our 'donors' we assign a rarity rating to each item, based on the system devised by Herman van Herwijnen

(1929 - 2004), renowned Dutch collector, author, and creator of Herman's Archive, a collection of 5,000 slide rule images on CD.

• RR = Rare - 1 of 25 collectors has one; it may take a year to find an example in the marketplace.

• RRR = Very Rare - only a few known to collectors; may be several years before it comes up for sale.

• RRRR = Extremely Rare - a museum piece; unlikely that an example will come up for sale.