| Name and Model Number | Felsenthal Altitude Correction Computer |
| Country of Origin | USA |
| Date of Manufacture | Box dated 1948. Probably used in WWII |
| Front Scales | Altitudes and temperatures |
| Back Scales | none |
| Scale Length | Spiral, about 48" |
| Type of Rule | Disc |
| Construction | Black fibrous material |
| Area of Use | Military |
| Comment | Attractive spiral scale circular rule made for U. S. Air Force. |
| Rarity | RR |
| Donor | Collection of Clay Castleberry |
| Match Number | 271 |
| 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. |