Full Details

Name and Model Number Keystone American
Bule Paper #1540A
Country of Origin Germany ---- DRP No (DP) 126499, in trough
Date of Manufacture Cursor c. 1915, Probably early 1920 to 1930
Front Scales A, B, CI, C D, K
Back Scales S, L, T back of slider
Scale Length 12.5 cm
Type of Rule Slide Rule
Construction Celluloid on Mahogany
Area of Use Generic
Comment Mahogany with groove in trough European style. K&E frameless with white flap type endpieces unlabeled black cardboard case. A very diverse slide rule made in Germany with a K&E classic cursor.
Rarity RR
Donor Collection of Clay Castleberry - California USA
Match Number 283
(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.