Full Details

Name and Model Number Ross Precision
Country of Origin U.S.A.
Date of Manufacture  
Front Scales 24 circle precision scale + rule for approximate calculation.
Back Scales sin scale
Scale Length 11.6 cm diameter
Type of Rule Disc
Construction Tin
Area of Use Generic
Rarity RR-RRR
Donor Collection of Rod Lovett
Match Number 34

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.