I once got a Swazi Lilangeni coin [1] in change from a machine at Paddington station. Could it have been one of those? As an entirely above board numismatic dealer selling them in bulk [2] says:

"they are lovely looking coins, bearing an uncanny resemblance to the British One Pound coin [...] All of the One Lilangeni coin attributes are exactly the same as the British One Pound coin."

[1] https://en.numista.com/catalogue/pieces29731.html

[2] https://www.alibaba.com/product-detail/One-Lilangeni-Coin-19...