When I started out to try to get a nice playing set I found a lot of the interlock chips; made in the 2940's they were transition chips between clay composition and plastic chips that splattered around after WWII. They are part plastic and part clay. My first set of chips was in 1946 in Injokern (Sp?) when I spent a birthday gift at a Navy commisary to the horror of my mother. I still have some of them.