| Name and Model Number | GRAPHOPLEX – 691 NEPERLOG HYPERBOLIC |
| Country of Origin | FRANCE |
| Date of Manufacture | abt. 1960 |
| Front Scales | L P Ch A B T<45° ST S C D Th Sh2 Sh1 |
| Back Scales | LL01 LL02 LL03 DF CF CIF K CI C D LL3 LL2 LL1 |
| Scale Length | 25 cm (10 inches) [ 338x48.7x4.2 mm ] |
| Type of Rule | Slide Rule |
| Construction | Plastic |
| Area of Use | Generic |
| Comment | Graphoplex, based in Paris, was the main slide rule manufacturer in France. Some slide rules were also redistributed to the USA via a Koh-I-Noor label. |
| Rarity | RRR |
| Donor | Collection of Gonzalo Martin, France |
| Match Number | 377 |
| 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. |