Second to having the guy go only through ebay message system. Have him open a case (if not already). Ebay will store ALL information that goes through the case including pictures. Phone calls are off the record.
edit: and also, looking at the pics, if he can get a closer pic of the collar - if corrosion / verdigris has been removed he has obviously changed the razor. I don't know if ebay has a policy about returning things after they have been tampered with by a buyer. IMO just looking at the pics of the cracking, it looks like it has been hammered to tighten with catastrophic failure.