In the UK, banks supply coins in clear plastic bags, but some foreign coins still get through! Unfortunately most of them are a lower face value than the British coins they were masquerading as! In the days of the old round brass £1 coins that circulated from 1983 to 2017, I found Sri Lanka 5 rupee coins, New Zealand dollars and EU 20c coins in pound coin bags! I've had a Hungarian 10-forint coin (the wrong shape!) in a £10 bag of 50p coins! On the other hand I've occasionally made a bit of money, when I've found US and Canadian quarters in bags of 10p coins. US dimes occasionally turn up in bags of 5p coins.
Of course I also sometimes get coins from Guernsey, Jersey, the Isle of Man, Gibraltar, St Helena and the Falkland Islands, which I'm always happy to add to my collection!