As a child, I actually once spent a half hour rubbing a penny on the sidewalk on its faces and edges until it was the size of a dime for a candy machine.
Made 9 cents profit, which worked out to 27 cents an hour.
Glad I didn't get caought.
Living pretty dangerously as a kid.
One time I cut the tag off of a mattress. (They are still looking for me 30 years later.)
I did the same except I used large tin-snips to remove the raised rim of the penny. I was more astounded that it actually worked than guilty that I had ripped off the 'system'.
I used them in an orange juice machine at school. School authorities made it known that they were aware of it and it had better stop. It did. They never let on what the actual conterfeit consisted of so there were no copy cat crimes. I would reimburse the school for the 50-60 cents, but the place was torn down in the late 60's.
Confession is good for the soul.
I feel better now...