Full Details

Name and Model Number	Keuffel & Esser Co. N4100
Country of Origin	USA
Date of Manufacture	Estimate 1920s
Front Scales	Unmarked stadia scales
Back Scales	None
Scale Length	25 cm (10 inches)
Type of Rule	Slide Rule
Construction	Celluloid on Mahogany – metal frame cursor – adjustable body
Area of Use	Topography
Comment	Used for stadia surveying calculations. Constructed on heavier Mahogany frame than earlier models
Rarity	RR
Donor	Collection of Clay Castleberry
Match Number	289
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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.