| Name and Model Number | Calculigraphe Model F-C |
| Country of Origin | France |
| Date of Manufacture | before 1878 |
| Front Scales | L, N^3 |
| Back Scales | none |
| Scale Length | 11.3 cm |
| Type of Rule | Watch Type |
| Construction | nickel or German silver |
| Area of Use | Generic |
| Comment | This is the model F-C with the castle logo rather than the opisometer on the more common model H-C.
There are fewer than 6 known in hands of collectors. |
| Rarity | RRR |
| Donor | Collection of Clay Castleberry |
| Match Number | 251 |
| 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. |