I knew a guy in college that was a starving chemistry major. He devised a formula/process that would etch down pennies to the size and weight of dimes. A soda or candy bar cost 25 cents. So 3 cents, etched, dropped in a machine, gave him a soda or candy bar and 5 cents back.
After a while, strange men started showing up on campus and hanging around the vending machines… and if you had trouble with a machine taking your change they seemed to be quite quick to “help” you.
