Full Details


Name and Model Number Keuffel & Esser Mystery 20 Inch
Country of Origin USA
Date of Manufacture 19343
Front Scales 20in / DF [ CF CIF C ] D | 50cm
Back Scales Slide: [ Unknown Scale in Degrees ] ; NBS Circular No. 47 Conversion Table
Scale Length 20" (50 cm)
Type of Rule Slide Rule
Construction Celluloid on mahogany
Area of Use Generic
Comment Mystery rule with no model number. Scales on front similar to older 4088-3;
scale on reverse of slide is calibrated in degrees and is folded at 31 34'.
Function of the reverse scale is unknown as is its reference point. Serial No. 460528.
Rarity RRR
Donor Collection of Dr. Paul J. Tarantolo Jr.
Match Number 27
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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.