Since the pins do not have collars that could be a clue that they are ivory, however, with the beveled edge and the line around the bevel makes me think that it may not be ivory.
If you want you can do a "hot pin" test which is to take a small pin and heat the tip to red hot and place it somewhere inconspicuous and if it melts it is probably a plastic of some sort. If it does not melt then is may be bone or ivory. If I can find my ivory ID stuff I will send it to you.