I was visiting my cousin in Seattle, I must have been 15. Everyone else went in while he “fixed the meter” I hung back and watched. He sat on the curb filing a penny on the concrete. Apparently if you file it so it fits in the dime slot the rough edge would catch and you could just keep spinning the dial to add the max time to the meter. Of course don’t choose one of the old copper ones or you’ll be there all night.

The repair shops must have hated that. Imagine having to take apart meter after meter to remove the stuck penny.