Full Details

Name and Model Number Léon Lalanne
Country of Origin France
Date of Manufacture circa 1850
Front Scales The slider is visible through two windows in the body of the slide rule.
The upper window handles trigonometric functions.
The lower window displays A,B,B and D scales in the normal nomenclature, and includes specialized gauge marks.
Back Scales The slider is visible through a single window. Two pairs of C and D scales are provided.
A wide range of gauge marks are also provided, in French, including parameters relating to molten metals
and conversion factors for measurements new and old.
Scale Length 247 mm (approx. 9.75”)
Type of Rule Slide Rule
Construction Cardboard and paper
Area of Use Other
Comment Probably used for metallurgy.
Rarity RRRR
Donor Collection of Trevor Catlow
Match Number 77

RR = Rare -- 1 of 25 collectors has one; it may take a year to find an example in the marketplace.   
RRR = Very rare -- only very few known to collectors; may take several years before one comes up for sale.   
RRRR = Extremely rare -- a museum piece; unlikely that an example will ever come up for sale.