Knowledge about solid gold vintage Omega Geneve

That appears to be a solid gold example. I don't believe that OMEGA produced plated versions of that model, though it's a bit outside of my (slightly earlier) period of expertise.

The crown does not appear to be original, as an aside.

If solid gold there should be hallmark somewhere often on bank of one of lugs. And also marked inside Caseback.
There are also references that had “gold filled” cases and Caseback can be gold color . But this should be indicated inside Caseback Sometimes gold filled is inscribed on side of case. This is common with US market cases.
I agree with @Tony C. this is probably solid gold but need to see inside to be sure.
Gold capped and gold plated watches have stainless Casebacks.
This is a sought after reference but this example has a lot of dial damage with bubbling which brings it down.

Omega plated a thin coat of gold on vintage Geneve, not 200 micron gold cap.
If you look under the lugs you cannot see any SS there and think it is solid gold but actually, it is gold plated.
Always look for hallmarks to confirm solid gold.
Here are some pictures to know more