I didn't know, until I found this and looked it up, that the UK Armed Forces used to have their own money. Soldiers were paid for about twenty years after the second world war in "Special Vouchers" to avoid the problems associated with being either paid in a local currency or being paid in Sterling - mostly about black marketeering and profiting from the then relatively high price of Sterling.
Of course, many people who read Steemit posts are also interested in currencies. I had no idea that we'd had such a widespread alternative currency (a kind of physical stablecoin pegged to the pound) in the recent past. It gives me lots to think about.