It might not be easy to tell if a single item might be a chess piece. For instance an item that has been frequently listed on ebay:
http://www.ivory4u.com/estate2/17cManOnBall.jpg
The figure really does look like a chess piece but it might be just a fine individual piece of carved ivory.
Here is one more example of the same line:
http://www.ivory4u.com/estate2/4511.jpg
Some netsukes are designed as chess pieces - in that case, wholes should help to tell. Some okimono figures very much resemble chess pieces.
Butrint chessman has been a subject of much discussion. Is it really a gaming piece or just an ornamental detail?
http://history.chess.free.fr/butrint.htm Might be a million dollar question :)
Ebay item 110052443587 is not a chess figure (although it is a really beautiful piece of ivory IMHO) but what if it had a turned base? Would you buy it as a chess piece in this case?
Thins get even more confusing with ancient pieces. Jon collects medieval and earlier gaming pieces (often archeological finds) - maybe he can shed some light on the topic. For instance, what about item 200045952413?