Yes, they are ivory. Technically you can't say ivory on eBay (political correctness, conservation bit). In a sense ivory is a type of bone. Worth the $100 price there now. Common in a sense, but all ivory is good.

How to distinguish ivory, bone and celluloid chip; and ivory fakes .
http://www.antiquegamblingchips.com/distinguish_iv_bon_cel.htm

I redid my page some, new pictures:
http://www.antiquegamblingchips.com/Ivories_JosephineB.htm

Robert