My early 1950's model 27 does not have any date stamps anywhere,not even on the stock. It would seem to be very well made and assembled, more Germanic than the later Milbro developed models.
I love the term ... BritishLeylandy, very apt. As an RAC patrol during the 70's to 00's I have worked on many of Longbridges finest and they were utter crap. Tolerances could be measured with a callender, nevermind a micrometer........l.o.l.

Pete.