I have two, although neither of them will work now. Back when Germany was East and West Germany, West Germany issued a 1-pfennig coin that was the same size as a Toronto (aluminum) subway token. I had a couple, as part of a world-coin collection, and I noticed the similarity in size but thought nothing of it. Then, I read in the local newspaper that some people had spray-painted pfennigs to look the same as an aluminum token and were slipping them in collection boxes. Circulated 1-pfennigs sold for a dime, while a token was about a buck back then. The second comes from the mid-1990s. The Canadian one-dollar coin was about the same size as the 50-cent piece. A fellow I knew found out that dropping a fifty-cent'er into a vending machine got him credit for a dollar; the machines couldn't tell the difference. He had a merry old time with his halves. Anyone else got any shenanigan stories?
I used to shine pennies with ketchup(long before I started collecting), and tell little kids they were made of solid gold. Surprising what little kids would believe back in the day.
Way back when, the circular knock-outs from electrical boxes were the same size as quarters. After filing off the little bit of connecting tab, plenty of free pin ball games and juke box music. Three games/songs for a slug. Those were the days!
Back in the 60`s I used to use Irish Halfcrowns in the coin operated cigarette machines in the UK. I got 20 cigarettes and Sixpence change, LOL I have long since given up on the ciggies though.