Many older casino dice do not have serial numbers on them. A few present day casinos do not use them now but most do. Do the dice in question have any cancelation marks on them? Reject dice are often canceled with "VOID" stamped into the 4 side, or a gold hotstamp "xx" or "O". Many reject dice can be seen to be unfinished if examined closely, or will be too perfect never having bounced down a table. Can you post or send a scan of the dice? espeialy the 2, 4, and 6 sides?