|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.
|Donor||Collection of Clay Castleberry|
(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.|