Thank you for the answer Monito1975. By the way, your watch is great,
The Eta 7751 is different from the Eta 7750 (more complicated, and much more expensive too!) If a genuine 7751 fitted in my rep Datora, I would do the swap. But as I said before, an original 7751 may cost more than 500 dollars, so I have to be sure. Buying a new Navitimer rep. could be a great alternative, but getting one of them must be complicated nowadays.
Thanks again for your help.