Yes A, the reason why I said that it is highly unlikely to be an ETA7750 is simply because I have not personally come across an ETA7750 modified to have a sec@6.. I know there are probably such things, but if and where they exist, they are likely works of members who purchased and modified them, and hence should be from an m2m sales and not purchased off any sites brand new. 600Euros is a grossly inflated price to pay for this watch, if it is what I think it is.
Ultimately, I am not Rolex expert, and the above are my personal 2 cents.