To elaborate, it’s really easy to forge “regular” coins and really attractive to forge high value coins.
For example, the 1 British Pound coin was, before the redesign, widely forged:
As of March 2014 there were an estimated 1,553 million of the original nickel-brass coins in circulation,[6] of which the Royal Mint estimated in 2014 that just over 3% were counterfeit.
Those buggers wouldn’t unlock supermarket trolleys, so you’d have to get rid of them at a McDonald’s, where the staff don’t look too close at the coinage.
To elaborate, it’s really easy to forge “regular” coins and really attractive to forge high value coins.
For example, the 1 British Pound coin was, before the redesign, widely forged:
https://en.wikipedia.org/wiki/One_pound_coin
(Note for any languages that use the comma as a decimal separator: 1,553 million is referring to 1.5 billion)
Those buggers wouldn’t unlock supermarket trolleys, so you’d have to get rid of them at a McDonald’s, where the staff don’t look too close at the coinage.
In the UK the key from a tin of corned beef will operate a trolley. Do with this information what you wish.