In US money, a penny is slightly larger than a 10 cent piece. When I was in high school, they had vending machines in a small shelter that dispensed apples, oranges and small tins of fruit juice for 10 cents. So, some kids would cut pennies down in the metal shop class and use them in the machines. These machines had several chain driven columns of plastic bucket bits that would be run around one step and the bottom bucket would be tipped to dump its contents out the delivery slot. Well, one day someone cut a penny a little out of round and it stuck so the apple juice column kept going and dumping the wee tins faster than they could be removed. Eventually, they backed up and one fell onto a contact strip, shorting it out and starting all the columns going. Apple, grape and orange juice, apples oranges and pears were dropping all over the place.
Pay phones at the time were made so that dropping in the money would enable the dial for making outgoing calls. It didn't take long to figure out that the dial operated a make/break switch at a certain rate. So, the poor kids would pick up the handset, wait for the dial tone and tap the receiver switch at the correct to dial the number they wanted. The trick was to give it one more tap than the digit you are dialing.
