Back in the 1970s, my parents owned a snack shop, which was extremely popular with young teenagers, due to the many video arcade games we had on the premises.
Fairly often, when my father was emptying the coin boxes from those machines, he would discover lots of silver quarters. He said that it was probably due to the kids raiding their parents coin stashes, and using the quarters to play the video games.
I don't remember what happened to all those silver quarters - although I'm sure they didn't end up in another video arcade.