ei8htohms
8555
it's a convoluted evolution
Hi Markus,
The movement started off as an evolution of the Omega 861 (Lemania 1873) as found in the most popular/famous Speedmaster model. Omega/Lemania added the automatic winding in such a way that dictated moving the minute counting mechanism to the dial side of the movement and placed it in the center. Omega called it the Cal. 1040 but I'm not 100% sure what Lemania called it at that point (it went through several other evolutions at that point, appearing in various automatic chronographs in the 70s (?)). At least some versions had a 135x designation. Here's a picture of one of the Omega versions (images borrowed shamelessly from the web).
Interestingly, the Heuer Regatta that used this movement was a flyback of sorts. It was a continuously running central seconds movement with a single button for flyback and the central minutes counter was turned into a 15 minute yacht-timer. The movement appears to have been a much simpler contruction in some ways, but clearly still based on the same Lemania caliber.
When Ebel stepped into the picture, I believe they changed two significant mechanisms in the movement. They moved the minutes counter from the center back to the three o'clock position (still on the dial side, via intermediate gearing) and changed the automatic system to something obviously heavily inspired by the Seiko Magic Lever. They may have also altered the calendar mechanisms in some way but I'm not sure about that. Actually, my knowledge of the kind of changes they implemented is based mostly on conjecture having seen earlier and late versions of the movement. I've never personally overhauled the Ebel version (although I have admired one through a display back before! 
).
Then when Breguet decided to reintroduce the Type XX in the mid-90s, Lemania created a flyback version based on the Ebel variant and removed the calendar (the Aeronavale was the first modern Type XX). Breguet called it the Cal. 582 and Lemania called it the Cal. 1378. Later they released the Transatlantique and called the version with calendar the Cal. 582Q (Lemania 1372). At some point in the 90s Breguet also stepped up the decorative finishing of the chronograph levers, adding straight graining and high polished beveling. One can guess this change corresponded to the introduction of one of the display back versions, but the updated parts were applied to all the models, with display backs or otherwise.
The most recent evolution is the Type XXI with the Cal. 584Q. They actually simplified the minutes counter by moving it back the center and added the 24 hour indication. Lemania doesn't really exist anymore to my knowledge so perhaps they didn't even have a Lemania designation for that development. At any rate, if they did, I don't have any idea what it is.
_john