Posted By:
T206Collector...tell him that I will pay him, but that I am going to have the card reslabbed by PSA or SGC. I would further tell the seller that if the card turns out to be improperly altered/non-authentic, that I will be returning it for a full refund.
He likely will balk and not want to follow-up with you, thus not requiring you to send payment and hopefully avoiding a negative feedback. No harm no foul. He may take you up on your offer, which is a plus.
I suspect if you can get a continuing dialogue going with the seller about your concerns that he will probably choose to find another unwitting buyer that won't be such a headache. He doesn't want the negative feedback either, and he certainly doesn't want any fraud or small claims court lawsuits.
But that's just me. I wouldn't have bid on a card slabbed by a strange third party grading source in the first instance, unless it was a good price for a trimmed card. There exists a presumption of guilt when a seller knowingly avoids PSA/SGC/GAI and their higher sales returns and instead opts to have their cards graded by an unknown entity.