Canada has no proof laws like the British system, and we had or have particular no arms industry except when Winchester bought out Cooey firearms, but back to the question, there are a few hundred I imagine commercila 455 MKII here in Canada atleast, I have one ,a good few friends have a few, great gun you picked up, any gun shipped to Canada has no proof marks other than S&W markings if ordered direct from S&W, so I would letter your gun to see if it shipped to Canada since you did pick it up from a very close location to our nations mutual border, cheers Dale Z in Canada!