These are slot machine tokens. They're the same size as actual coins and were meant to be used in amusement arcades. The idea was that if you paid out in tokens, people would be more likely to put them back in than go to the trouble of getting them converted into real money. It also helped with the arcade's finances, because there wasn't dead money sitting around inside the slot machines that couldn't be spent. Some arcades wouldn't exchange the tokens for money, only prizes (which is how wins at Bingo were usually converted).
Vending machine owners didn't like these tokens because people would use them there. You couldn't easily pass them off in a shop, but in anything else that accepted coins — such as gas meters — they were fair game. If you were caught, you could claim you'd been duped by some other shop when you were in a hurry and didn't check your change.
We didn't have these in the amusement arcade I worked in. They were expensive to get made up, difficult to separate from actual coins, a annoyed day trippers and were pain to convert into money when the customer asked for it. The tokens my dad found were therefore from arcades in other towns.
If you ever need metal game money and don't care what it looks like, you can buy similar tokens online for only slightly more than the value of the coins they copy.