send the serial# off of the case to Omega, they will confirm authenticity. Get that going in the meantime.
http://www.omegawatches.com/customer-service/contact-us
the clasp looks like it could be gen to me, and i'm staring at my gen as we speak. Its not as sharp as the rep laser etched clasps, but neither are gens. Yours has a softer look.
Here's mine, a 2009 electric blue model.
Yours appears to be an older model, the Omega anti-counterfeiting etch is missing from the caseback, but again, older models don't have it.
Here it is on mine, under the seamonster.
If you could pop the divers extension out and let me see a shot of it from the underside, that would help. They typically miss the bevelled lip that go's under the clasp bar on the reps, thats why they don't always snap shut as nicely.