Full Details

Name and Model Number	Keuffel & Esser # 4071
Country of Origin	USA
Date of Manufacture	1972
Front Scales	A B C D
Back Scales	A BI CI D
Scale Length	25 cm (10 inches)
Type of Rule	Slide Rule
Construction	Celluloid on Mahogany , frameless cursor, open edges, adjustable end frames
Area of Use	Generic
Comment	Probably second version after Cox 1891 patent version
Rarity	RR
Donor	Collection of Clay Castleberry
Match Number	288
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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.