Full Details

Name and Model Number Keuffel & Esser 4079
Cox Duplex
Country of Origin USA
Date of Manufacture c. 1900 - 1906
Front Scales A [ B C ] D
Back Scales A [BI CI] D
Scale Length 50 cm
Type of Rule Slide Rule
Construction Open frame mahogany; celluloid laminate. Metal framed glass cursor.
Area of Use Generic
Comment No model number on slide rule. Model #4079 determined by matching the slide rule attributes with K&E catalog descriptions.
Non-adjustable riveted end posts. Stamped with "Keuffel & Esser Co". & "Pat. Oct. 6, 1891" (the Cox patent).
This is an example of the first duplex slide rule.
Rarity RRR
Donor Collection of Ed Chamberlain
Match Number 135
(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.