They all have 16mm inside width?
It would be worth taking a look at the ‘parts for sale’ section. Plenty of buckles have been offered there to get an idea of overall value.
There’s also the huge buckles thread.
https://omegaforums.net/threads/about-omega-buckles.37347/
The GP one that says Stainless steel on back is fake. Others look original
In my opinion there are several that are not so attractive not sure its worth paying a premium for the lot.
The SS later MG versions can be found for $50-75 if you’re patient.