US heads were seldom "stamped" casting numbers were added in the core boxes prior to casting. Ford 8BA would have been used through 1951 with some exceptions in USA then EAB or 8RT for trucks was used through 1953. Canadian heads had "C" added most times but there were aluminum heads and cast iron ones and Mercury/truck variations just like there were here in the US. C8BA, C8CM (mercury), C1CM, Etc. I haven't seen too many Canadian engines down here in Texas but there are likely a few. I wouldn't be too surprized if they didn't have casting marks in the places that the US heads generally have.
Mercury Meteors had the C8BA engine in 1950 unless someone put something else in it. I've seen all sorts of other casting numbers on heads and I have never had anyone explain to me what they mean. I figure the guys that cast them back in the day were likely the only ones that might have know what the meaning was. Canada haveing Ford dealers and Mercury dealers separate may have had casting number differences to have a Mercury difference from Ford but I really couldn't tell you for sure. We would need someone with a lot of Canadian Ford/Mercury experience to have a better idea.