The Sportsman in London had an entire run of small crown chips in US dollars, and I have a 50c large key as well. My memory isn't what it used to be, but I'm sure I read somewhere, perhaps on this board, that the Sportsman used US currency at one time. Oddly enough, my small crown 50p has a blank reverse also, which leads me to beleive that all the 50p must be like that. The $1, $5, and $25 I have are normal.