Mysterious Rare Case Back

Hello All,

I am looking at aquiring an unusual piece from a private seller. These F1's were commissioned for the crew of the Round Europe Yacht Race in 1987.

I have found auction catalogues showing this model but have found little information on Calibre 11 about this specific iteration.

The only thing that worries me is the case back. The reference number is skewed which looks to me like either a fake or non genuine case back replacement.
The internal signature is also different to other 80's F1's i have seen.

Any thoughts welcome.

Thanks,

Johnny

Im afraid I cant help but just have to say, that is one really cool F1

I'm not an F1 expert, but that case back looks a bit shonky to me. Hopefully some of the others here will chime in.