Full Details

Name and Model Number Aston & Mander
Country of Origin UK
Date of Manufacture  
Front Scales Tonnage/Gauge Points, Extreme Breadth/ Length for Tonnage
Back Scales None
Scale Length  
Type of Rule Slide Rule
Construction Wood
Area of Use Other
Comment Naval architects tonnage calculator.
Carries the name G L Watson & Co. Naval architects and surveyors, Glasgow, Scotland on the back.
Rarity RRR
Donor Collection of Colin Barnes
Match Number 84

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.