Full Details

Name and Model Number Dempster RotaRule
Model AA with Magnifier
Country of Origin USA
Date of Manufacture ~1943 or 1944
Front Scales K, A, D, C, CI, CIF, S, C, ST, T, CT, G (scales), B, F/i
Back Scales L, LL%, LL1, LL2, LL3, C, [V1, V2, DLL, D]
Scale Length 50" (127cm)
Type of Rule Disc
Construction Plastic 5.25" (13cm) diameter
Area of Use Other
Comment For precision basic math and stadia calculations. Has unique modified spiral scales.
Rarity RR-RRR
Donor Collection of Richard Davis
Match Number 49
(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.