Maybe there's a business opportunity for an online verification service? You identified the Finnish watch as having issues from a few pictures so it's likely even more could be done over something like Skype. Any dealer could start a Skype call to your trained staff who could offer an opinion (chargeable, of course). You can even see that it wouldn't take long for the suggestion that a watch brought in to a dealer was going to be referred for verification would see them leg it out of the door.