I think it is a fake but its a pretty good one. That looks like a 7750 clone movement with convincing rotor engraving, if it is coaxial as stated it should instead be a 3313 or 3330 presumably both of which looks quite different. The dial text looks a bit off and as noted above the smoking gun is the Seamaster back on a DV. Though it must be said back in the day Omega had form for mixed branding. Not so much during the era this is supposedly from.
EDIT: it is a copy of model 4841.31.32 from circa 2005-2010 which had the 3313 movement. It's deffo fake.