Full Details

Name and Model Number Holdman Slide Rule
Steam Valve Adjustment
Country of Origin USA
Date of Manufacture Patent 1938-1940
Front Scales Various. Scales are not logarithmic
Back Scales Data chart
Scale Length 6" and 8"
Type of Rule Slide Rule
Construction Brass colored steel
Area of Use Technical
Comment For adjusting slide valves on steam engines and locomotives.
One other example known to exist.
See donor's article in Journal of the Oughtred Society, Vol. 21, No. 2, Fall 2012.
Rarity RRRR
Donor Collection of Clay Castleberry
Match Number 243
(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.