Full Details

Name and Model Number Martini 3991
Country of Origin Italy
Date of Manufacture  
Front Scales K,A/B,CI,C/D,L
Back Scales S,ST,T
Scale Length 125mm
Type of Rule Slide Rule
Construction Plastic
Area of Use Generic
Rarity RR
Donor Collection of Colin Barnes
Match Number 83

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.