The watch looks legit. For valuation, I'd suggest researching previous sales on similar gold-filled SMDV models, either in the forum sales listings or auctions.
Personally, I don't collect gold-plated/gold-filled watches and wouldn't even pay the $600 that is already bid. Unfortunately, the high price of gold is driving up prices of watches with solid gold cases, so people who want a gold-colored watch are overpaying for gold-filled/gold-plated watches, which have generally been considered entry-level watches, not really made to last.