Full Details

Name and Model Number Charles Bessler / K&E
Projection Rule
Country of Origin USA
Date of Manufacture Estimated 1950ís
Front Scales A B DI C D K
Back Scales None
Scale Length 20 cm (8 inches)
Type of Rule Slide Rule
Construction Clear Plastic
Area of Use Generic
Comment Projection Slide Rule for class room use.
Rarity RRR
Donor Collection of Clay Castleberry
Match Number 295
(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.