Most of the value in a pre-owned watch is in what you cannot see in the photograph: the state of the movement, the originality of the dial and the honesty of the seller.
Ask for the timing sheet
Any serious dealer can tell you the amplitude and rate of a watch they sell. If they cannot, it has not been checked.
Ask what has been replaced
Replaced crystals and gaskets are normal service items; ask whether the originals were kept. A replaced crown, dial or hands changes the watch, and should change the price.
Ask whether it has been polished
Polishing removes metal. A case that has been polished many times loses its sharp edges for good. We prefer to sell watches with their marks and let you decide.
We would rather show you a scratch than hide a softened bevel.