In reply to DaveHK:
> They don't tend to be made, it tends to be other coins being repurposed. We regularly used to find Swaziland Lilangenis in our vending machines. They passed for £1 coins at the time but were worth about 12p as I recall. Obviously needs to be a pretty big operation to make much money on that!
I remember at school it had been worked out that the foil from chocolate pennies could be used to uprate the value of coins in one of the vending machines. I think it was 10p to 50p, but it sometimes confused the machine and you got about £2. It was a surprisingly long time before they took that machine out of commission.
At one of my first workplaces, they had a card system for the canteen, which occasionally gave you £20 when you tried to load on a fiver. It was eventually worked out that it was a bank of Scotland fiver, castle side up and one particular end first that did it, and lunch became very cheap for those in the know.