I just purchased a collection of Indo-Tibetan stone beads that were originally acquired in the 1970s. Included are some Dzi beads capped in repousse brass. I am wondering how to date the stones. It is my understanding that back then, older beads were capped in brass and silver or silver metal in Nepal for western consumption. Were Dzi beads being mass produced in the 60s and 70s as they are today or might they be older? Any opinions as to their age?