Full Details

Name and Model Number	Keuffel & Esser 4040
Country of Origin	USA
Date of Manufacture	1901
Front Scales	10 inch /, A [ B C ] D, | 27 cm
Back Scales	Slide: [ S L T ], Rule: Conversion table
Scale Length	25 cm
Type of Rule	Slide Rule
Construction	Celluloid on mahogany with brass chisel cursor
Area of Use	Generic
Comment	Believed to be the forerunner of the popular 4041.
Rarity	RR
Donor	Collection of Clay Castleberry
Match Number	234
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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.