Full Details

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.
Rarity RR-RRR
Donor Collection of Ed Chamberlain
Match Number 158
(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.