Full Details

Name and Model Number Palmer's Computing Scale
Country of Origin U.S.A.
Date of Manufacture ~1843
Front Scales 2 single-cycle logarithmic
Back Scales None
Scale Length ~ 12 ins square
Type of Rule Disc
Construction Cardboard
Area of Use Generic
Comment Gauge points indicate that it was designed for area
and financial calculations.
Rarity RRR
Donor Collection of Colin Barnes
Match Number 32

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.