The info in the first post detailing the information stamped on the side of the crate, compared to the serial numbers on the guns, in conjunction with the information already known about the Type 56 already would seem to indicate that the research is sound.
Parts might be made all over the place, but there is nothing to say that the stamping would happen other than during assembly of the complete gun. Parts might be made all over, but assembly is done in one specific plant per gun. Parts from many factories, shipped to and assembled in one specific factory.