Hi,
On a legit watch with a 8500 caliber there should be a red “8500” engraved on the oscillating weight and a serial number engraved on both the balance bridge (hidden by the oscillating weight on the picture) and under the bottom-left case lug, not present on the picture. It could have been photoshopped out, though, but I guess there is no way to tell for sure unless you know for a fact that’s what the dealer usually does, or unless you see the real thing.
On a legit watch with a 8500 caliber there should be a red “8500” engraved on the oscillating weight and a serial number engraved on both the balance bridge (hidden by the oscillating weight on the picture) and under the bottom-left case lug, not present on the picture. It could have been photoshopped out, though, but I guess there is no way to tell for sure unless you know for a fact that’s what the dealer usually does, or unless you see the real thing.