This charming Thermidor twin register chronograph came in for a service recently. What’s interesting about this watch is it’s powered by a Calibre 12 movement, the calibre 11 which preceded it was developed by the ‘Chronomatic’ partnership of Heuer, Breitling, Hamilton-Buren and Dubois-Depraz in an attempt to be the first to the market with an automatic winding chronograph. The calibre 11 was revealed to the press on March 3 1969 in press conferences in NewYork and Geneva and was manufactured until about 1973. The calibre 12 was introduced in 1971 and was produced until 1980. The calibre 12 addressed a few of the issues that appeared with the calibre 11’s, modifications included using lighter jumper springs, a weaker mainspring to drive a redesigned date mechanism, some strengthening of various levers and hammers and a faster beat rate of 21,600 as opposed to the cal 11’s 19,800. This Thermidor cased example has a typically bright seventies style dial and handset design, and you can also see one of the cal 11/12’s more striking features, a 9 o’clock crown.