When did the shift occur to so much silver bullion being produced in 999+ standard, even amounts (1 oz, 5 oz, 10 oz, 100 oz, etc)? It seems to be pretty recent as in the 2000s. It seems pretty rare nowadays to find much sterling silver, for instance, in a random medal or coin with an ASW of .8-something, or whatever. How desired is this older, random silver from 70s, 80s, etc.?