I would call them 1 ounce silver rounds or silver art rounds. Anyone can have these made and you could have your own mint mark on them. I'm sure they were issued for special reason. In the 70's collecting silver bars and rounds was popular. Most of the time these are priced at a few dollar(s)($1 to $5) over current silver price. Right now silver is $6.77 an ounce. I have fond that these make great additions when you display your collections at shows. Just kinda adds something to it. Pretty neat, I have a few I have kept. My are different than yours. Hope this helps!

Robert