Full Details

Name and Model Number Martin’s Calculating Rule
Country of Origin England
Date of Manufacture 1918+
Front Scales Length 1’to 700’, Breadth 1”to 100”, Thickness 1/10” to 12”, Rate 1/8/- to 100/-,
Amount £1 to £200
Back Scales Length 1’to 700’, Superficial Scale, Conversion Scale”, Rate 1d- to 60/-,
Amount £1 to £200
Scale Length 72.5cm
Type of Rule Slide Rule
Construction Box with Brass Straps
Area of Use Other
Comment Costings calculations, primarily used in ship building.
Patent GB 135671 1918. Made by C.T. Cooper & Sons Ltd.
Rarity RRR
Donor Collection of Peter Fox
Match Number 61

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.