While reviewing my coins in a pocket, found out that one of the coins was a little bit different from the rest. It appeared that Australian 50 cents looks almost identical to the one from Fiji!
When you compare exchange rate, it will be clear that Fijian dollar is roughly 35% cheaper than Australian one.
Which means, whoever gave me a change with Fijian 50 cents won ~35% by this "direct exchange".
Does it mean we can import Fijian coins and use it here, in Australia, having 35% discount on goods?
I don't think it will be feasible, however on a small scale - well, somebody gave me a change while I couldn't differenciate the currency 😁