Full Details

Name and Model Number Chadwick’s rule
Country of Origin U.K.
Date of Manufacture  ~1905
Front Scales Soho/Routledge variant
Back Scales Tables of general engineering facts and figures
Scale Length 11”
Type of Rule Rule
Construction Boxwood & German silver
Area of Use Technical
Comment Used for engineering calculations.
Chadwick’s rule is possibly the last design of 2-foot, 2-fold slide rule.
J. Chadwick, an engineer from Manchester, published his "Slide Rule Instructor
for the Instruction on Chadwick’s Improved Slide Rule" possibly as late as 1905.
This beautiful example has no maker’s name on it and another quite unusual
collection of gauge points and is amongst the most unusual of the 2-2 slide rules.
Rarity RRR
Donor Collection of an English gentleman
Match Number 44

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.