The ebay seller describes the set below as an "Antique Ivory Poker Chip Set". They look like cheap plastic chips to me.

Interestingly he mentions "Very few cracks if any. Nicely preserved piece." That would imply that some pieces have cracks. Again, I doubt it.

Here is the auction: http://cgi.ebay.com/Anique-Ivory-Poker-Chip-Set_W0QQitemZ280086230279QQihZ018QQcategoryZ63756QQrdZ1QQcmdZViewItem

Of course being the cynical guy I am, I don't believe the mistake (if it is one) was an accident.