Many here will know the difference between an integrated chronograph (e.g. El Primero) and a piggy back movement, like the Chronomatic (Cal. 11/ 12/ 14/ 15) series. Essentially, the latter takes a base movement used for a 3-hand watch and bolts a chronograph module on top. This great photo that Abel took of my watch shows the two parts really well- I'd never seen it before In the case of the Chronomatic movement, the base movement was designed by Buren, which was bought by Hamilton in 1966. You can see the micro-rotor above- very different to the large rotor used on the Calibre 1887 for example. And the second component is the Chronograph module designed by Dubois-Depraz, who also make the chronograph module for many of TAG Heuer's movements today, including the new Calibre 12 used in the Monaco- an entirely different movement, but with the same name.
Great pic - thanks David and Abel for sharing! Like you, David, I understood the general design but had never seen the two parts separated before. Great stuff!
Would this have been one of the first uses of a piggyback system? I know its fairly common today not just for chronographs but for annual calendars and the like, even the Rolex Skydweller supposedly is a piggyback system of sorts but I'd imagine when this came it it was a fairly new way of looking at the problem. Did they use the base movement in many watches other than Buren without the chrono module?
Here's some more...typically the chronograph module is normally not taken apart completely when servicing. This one is the "economic" version of the Caliber 15, being the Caliber 15.