It may actually be the same age. BSA, like any business, didn't want to get stuck with redundant immovable spare parts, and when some storeman pointed out in 1952 that he still had two gross of the older and smaller headset bearings left, the foreman told the frame shop that he wanted the smaller-sized headstock for the next two hundred frames. Problem solved.
This assumes that the numbers stamped on the frame are consistent with 1952, obviously.