Got a very quick response from the seller saying it was part of a 'job lot' and thanking me for pointing out his mistake. He did appear to be genuine. Actually, I also think he was mistaken because I wouldn't have thought anyone knowingly selling a fake such as this as genuine, would be stupid enough to take pictures that show the thickness of the coin - that's a sure sign of naivety rather than intentional fraud. Good on him though, he's going to relist it.