Full Details

Name and Model Number K&E Sperry Type 3
Country of Origin USA?
Date of Manufacture c1909 - 1939
Front Scales ‘S’ scale: L,C,√√ (Square root – 2 circles)
Back Scales ‘L’ scale: 3 circles log scale
Scale Length Approx 12”.
Type of Rule Watch Type
Construction Metal, engraved metal dials
Area of Use Generic
Comment This is the K&E’s “Sperry/Lange” pocket-watch calculator with its very iconic “concentric nuts” winders
which came in a number of versions over about 30 years. K&E continued to use the Model 4017 number through
to 1939 with two different US Patent dates on the front face, and also as the Model 4018 for a relatively
short time between 1909 and 1927 called the “K&E Calculator” with “Pat Appd. For”. Examples are serial numbered.
Please tell us if you have an example and let us have the serial number and type.
Rarity RR
Donor Collection of Peter Hopp
Match Number 49

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.