First auto chronograph movement
Was Zenith El Primero really the first automatic chronograph movement?
Well, technically no, and yet one could argue that indeed it was.
While automatic movements became frequent during the 50s, the automatic chronograph movement did not appear until very late in the 60s (1969). At the time it was thought an impossible task for a single house to achieve the development of an auto-chrono movement on the grounds of insufficient technology, manpower and budget. Therefore, in the pursuit of such a noble horological purpose, alliances were made and two different groups appeared. One of such group was form by Breitling, Hamilton/Bren, Heuer/Leonidas and Dubois-Dpraz, and the second competitor in the race was formed by the Zenith-Movado group.
The Breitling group assigned a task division. Bren developed the basic movement, which consisted of an Intramatic 1280 (or 1322?*) caliber with an eccentrically mounted, small massive rotor. Dubois-Dpraz developed the chronograph module, which was based on module #8510. And finally, Breitling, Hamilton and Heuer assembled the parts, producing caliber 11 (and claiming the glory).
In the meanwhile, Zenith had bought Matel (a company specialized on chrono movements) from Universal Geneve, and assigned them the task of developing the idea of an auto-chrono for Zenith.
By 1969 both groups had accomplished their objectives. The Breitling group announced their caliber 11 on March 3, while Zenith announced their El Primero (based on a PHC 3019 caliber) some time in September of that year.
Indeed the Breitling group did developed caliber 11 half a year earlier than Zenith; however, the later argued that while caliber 11 was the first (here is the trick) chronograph module with automatic winding, it was them (Zenith) who had actually developed the first fully integrated chronograph automatic winding movement. Thus El Primero (The First).

Some other interesting info I came across.
The caliber 11 had the crown on the left and the chronograph pushers on the right, two registers and day of the month. It did not have a continuos second hand, but just the chrono second hand. The chrono module was attached to the watch movement by only three screws. (There is a great illustration of this movement, as well as the Zenith movement, in pages 60 and 61 of the book Chronograph. Wristwatches to Stop Time by Gerd-R Lang and Reinhard Meis).
The caliber 11 had two shortcomings. The micro-rotor would not work well enough and therefore winding was difficult, and the main spring was weak so the watch would easily stop.
It seems that Valjoux might have developed its 7740 caliber based on caliber 11, but this movement disappeared when Valjoux was later bought by ETA.
El Primero movement disappeared in1972 when Zenith was acquired by Radio Zenith Corp., and later reintroduced in 1982.
A last piece of info is that Seiko might have announced a chronograph automatic movement (based on a 6139 caliber) on May of 1969, which would made Zeniths El Primero el segundo o el tercero (the second or third). (Anybody out there with more info on this?)