I just inspected one of my (2) Professionals that is apart, and there is no date, since it was on gasket material that I have stripped off. Fortunately, I had photographed it earlier:
I’m guessing that the “041262” signifies 4 December 1962. Ofir thought he read a 1952 date on his Professional, but I think that was actually “62”. In fact, his photos show two dates, the other one being a March 1962 date.
It is noteworthy that the date is stamped on the gasket strip, which suggests that it was dated when the instrument was being put together.