One Coin
Coca Cola sold its product for 5c, for 70 years. Mainly because the vending machines took a nickel, and they wanted to stick to the One Coin rule.
This is one of the ways they wanted to solve it: They asked the US Treasury to mint a 7.5c coin.
To create a coin, just for them, to stick to the One Coin rule.
When I am working with a problem — I wonder which out there One Coin request I could make.