Full Details

Name and Model Number Halden Calculex Desk Model
Country of Origin England
Date of Manufacture c. 1918
Front Scales L, A [ B, C(Square Root of B) ]
Back Scales Degrees A [ BI, N(Cube Root of BI) ]
Scale Length 10.2" (26 cm)
Type of Rule Disc
Construction Metal with paper scales and glass windows.
Area of Use Generic
Comment Large scale (5 diameter) version of the popular Halden Calculex.
Double sided pocket watch calculator with front and rear rotatable inner scale discs.
Front and rear glasses have inscribed cursor lines and are rotatable.
Handles on the center hub aid in turning the inner discs.
Rarity RR
Donor Collection of Dr. Paul J. Tarantolo Jr.
Match Number 30
(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.