which is housed in the GP ..."basically a 7750". It has been thoroughly reworked and instead of the stamped cams arrangement for the chronograph functions, it has two column wheels. Sure it is not a thoroughbred a la 13ZN but it is certainly not your run-of-the-mill caliber. There is more to this mouvement in my opinion, much more.
I have found this link on the net, for your perusal: grail-watch.com
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Thank you for the very nice picture.
Cheers
Francois