Nice and rare pocket watch with slide rule calculator.
Diameter is 58mm, height without bow is 77mm
Patented and made by Meyrat & Perdrizet, Doubs, France, circa 1890.
This watch is the first true combination of time piece and slide rule.
With it one can make a wide range of mathematical operations - multiplications, proportions, squaring, rooting, etc. Watch comes with recently printed manual in French.
These watches were producing from 1880s till the very early of 1900s, with overall about 500 pieces ever produced.
Very this piece bears serial number 222 and dates probably to 1890s.
The watch appears to be in good condition.
The rule scale is slightly tarnished.
An enamel dial seems to be in good condition.
The movement functions as it should, though time keeping is not guaranteed.