Full Details

Name and Model Number Keuffel & Esser N 4102
Surveyors Duplex
Country of Origin USA
Date of Manufacture  
Front Scales D, sine d, osl&h, c, Tan, Tan I, Az
Back Scales Vert Sin2a, A, B, CI, C, D Hoe. Cos sq. a
Scale Length 20 inches
Type of Rule Slide Rule
Construction Celluloid on redwood
Area of Use Topography
Comment Ive seen very few with original case- great rule see JOS articles by Richard Hughes
Rarity RRR
Donor Collection of Clay Castleberry - California USA
Match Number 273
(Click Picture for Details)

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.