| Name and Model Number | LaFay Helice a Calcul Models 1 & 2 |
| Country of Origin | France |
| Date of Manufacture | 1930s & 1940s |
| Front Scales | Spiral on cylinder |
| Back Scales | none |
| Scale Length | 85 cm (Model 1), 250 cm (Model 2) |
| Type of Rule | Cylinder |
| Construction | Heavy card stock tube with metal end caps, a clear plastic sliding sleeve and 2 sliding indicators. Model 1 is 10 cm long & 2.7 cm diameter; Model 2 is 20 cm long & 6.8 cm diameter. |
| Area of Use | Generic |
| Comment | Simple construction with a 50 revolution spiral scale on a cardstock tube. Patented in France in October, 1931 by M. Jean Antoine LaFay, Loire, France. Advertising for the LaFay Helice a Calcul appeared as late as 1945. Can be used for multiplication and division and for determining the logarithm of a number.
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| Rarity | RR-RRR |
| Donor | Collection of Ed Chamberlain |
| Match Number | 158 |
| 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. |