I would guess this is a fake. The loose observatory medallions are available for sale, so would not be too difficult to match to a back.
Rather than a cast piece, it almost looks as if the stars were stamped from the reverse side. Al, just for education, would a watchmaker normally mention these concerns or remain passive unless asked?
I can't see the pics (work computer) but I thought the gold on stainless medallions were stamped, not cast.
Available separately? I've been looking for about a year to replace one that someone pried off a Constellation 755.0802, no luck anywhere. They're gold and more or less worth melting down to some people. Omega want £260/$430 for a replacement back, so if you have a source, I'd love to know about it. And I would guess that Al's back is a fake, myself. Or else someone has attacked it with some enthusiasm.
They are stamped (from 14k gold sheet), not cast. Hoi has done the research . This back is a real oddity. If it was a "fake", it would have fake Omega factory inscriptions on the inside too, surely? And probably some attempt at perlage. From the amount of wear on it, it has been on the watch a long time.
Thanks for the input guys. The issue I'm having with this one is that the case back is binding on the rotor, so it won't wind while being worn (or on the test winder). Kind of threw me not seeing any marking on the inside of the case - not sure I have seen an Omega case back with no markings before. And yes of course I will inform the owner about this... Cheers, Al
If that is the case when the back is fitted with the correct gasket, it would certainly suggest that the back is not an Omega part - not even a service issue.
These are not, mine just a picture from a dealer. So I don't know if they are original. They do look worn.