Full Details

Name and Model Number Controller Calculator KG,
prototype 30 cm circular
slide rule
Country of Origin Germany
Date of Manufacture 1960s (estimated)
Front Scales C [D A K ]
Back Scales Weights and measures conversion tables
Scale Length 82 cm
Type of Rule Disc
Construction Aluminum alloy, celluloid cursor
Area of Use Generic
Comment This is apparently an unreleased prototype for a 30 cm diameter model that extends
the familiar range of Controller circular slide rules (comprising 7.5, 11 and 20 cm
For details see https://www.nzeldes.com/HOC/Controllers.htm
Rarity RRRR
Donor Collection of Nathan Zeldes
Match Number 414
(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.