Approx. Ø61mm, original nickel case, signed Meyrat & Perdrizet, factory glazing, cylinder inhibition, enamel dial, 2 rotatable calculator scales, manageable and well preserved, elevator spring still works, but urgently needs service, very rarely. The watch is identical to all other watches of this type produced by Alse Beaudroit Fabricant, Seloncourt (Doubs), under which Meyrat & Perdrizet applied for their watches with a computer. See the antiquorum auctions: New York, 20. June 1988, Lot 25, and Geneva, 17. ==References== There are 2 versions, with and without central second. Meyrat & Perdrizet was a French inventor's association, which became known through the groundbreaking development of the first pocket watch with integrated calculator (pendant to the calculator). This invention is considered to be the direct historical precursor of modern calculator clocks (such as the famous Breitling Navitimer). It allowed engineers, scientists and merchants to make mathematical calculations directly on their watch – long before the age of electronic calculators.