Full Details

Name and Model Number Simpson’s rule
Country of Origin UK
Date of Manufacture c1905
Front Scales Noble scales and tables
Back Scales Routledge engineering with gauge points inc Aluminium, conversion factors,
no steam gauge points
Scale Length 11”
Type of Rule Other
Construction Boxwood & German silver
Area of Use Other
Comment A 2-foot, 2-fold rule used in Engineering.
Abraham Simpson’s slide rule from sometime in the early 20th century is a strange mixture
of Routledge engineering and Noble’s designs of engineering 2-foot, 2-fold slide rules.
Engineering calculation is carried out on the one side; the second allows weight of steel
sheet etc to be done as on a Noble rule. Simpson included some calculations not possible
on the other two designs. Alfred Harper of Birmingham (1900 – 1925) is not a well known maker,
the factory burned down in 1925.
Rarity RRR
Donor Collection of an English gentleman
Match Number 66

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.