Full Details

Name and Model Number K&E Sperry Type 2
Country of Origin USA?
Date of Manufacture c1906?
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
Area of Use Generic
Comment This is the earliest form of K&E’s “Sperry” pocket-watch calculator,
and came in two versions, Model 4016 where the two dials are revolved at
a different rate (front to back) when the crown is rotated, and the model 4017
where the two dials rotate at the same speed.
It is not obvious by looking at the devices which model it is; the dials must be
rotated and observed. Pressing either of the push buttons and rotating the crown
turns the hands. Examples are serial numbered.
Please tell us if you have an example and let us have the serial number and type.
Rarity RRR
Donor Collection of an American Gentleman
Match Number 48

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.