The UK has a large market in coin-operated gambling machines - there are heavily-regulated low-stakes ones in all kinds of non-casino locations and, I think, higher-stakes ones in legal betting shops.
A relative who works in the industry told me he sees large numbers of counterfeit pound coins. I would guess counterfeiters might launder coins through machines. Or even, though I've never seen it, sell discount coins directly to gamblers? In any case machine recognition would be a high priority. The machines in question would be relatively unsophisticated ones with a thickness gauge and a 'ski jump' that effectively checks the weight.