| 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 |
| Thumbnail (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. |