Full Details

Name and Model Number Gebr. Wichamann Model 1399
Country of Origin Germany
Date of Manufacture ~ 1914 1930?
Front Scales L.C/D,√,√(2 circles)
Back Scales Tan,C/R,3√ (3 circles)
Scale Length Approx 16cm.
Type of Rule Watch Type
Construction Metal with celluloid lenses, rotated using the thumb
Area of Use Generic
Comment Quite idiosyncratic version of the Calculex with a pocket-watch
winder to rotate the centre scales on both sides
Rarity RRR
Donor Collection of Peter Hopp
Match Number 43

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.