That is called Double O buckshot -OO buckshot. Largest size shot typicaly used. There are 13 of those in a standard 2 3/4" 12 gauge shotgun shell. Usually for deer hunting. The little shotgun shells the police use have 7 of those, and less gunpowder. They are good for sling shots too. Since lead doesnt corrode much, they could be modern, hard to say, but they look pretty shiny to me!