I used to think, because it was nail polish, that it was caused by bored girls. However, later on I was told it it was a way to mark "house" quarters. A malt shop or bar, etc. would use painted quarters when the amchines were silent as a means to get patrons to use the machines. When the owner emptied the cash box he/she could always tell how much they made vs. the marked quarters they put in.

Any other stories?

Jim