Full Details

Name and Model Number Keuffel & +Esser 4061-T
With Column Cursor, 1915
Country of Origin USA
Date of Manufacture 1915
Front Scales A B S C D
Back Scales A BI T CI C D L
Scale Length 5"
Type of Rule Slide Rule
Construction Celluloid on mahogany
Area of Use Generic
Rarity RRR
Donor Collection of Clay Castleberry
Match Number 255
(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.