The Noctilux f1 glass has always been made in Canada. Some years ago the former Elcan plant in Midland decided that they did not want to continue with the production of the barrels and assembly ( it is a very small production - a couple of 100 lenses/year). Now the glass is shipped to Solms and the lenses are assembled there.
Since the 60's, most of the M-lenses were Canadian designs and manufacture. Dr Mandler, one of the premium lens designers of all time worked in Midland. He designed more than 40 of the Leica M and R lenses, some of which still are considered the best of the bunch (Summicron 35, Noctilux, Summilux 75, Summicron 90 Apo-Asph, 100 Apo-Elmarit R, 180 Apo-Telyt R just to name few).
Often lenses were designed and assembled in Canada without the rear focussing mount and shipped to Germany for the rear mount -which was duly engraved "Made in Germany". This was a way to avoid import duty on finished lenses, which was considerably higher on these rather than on "Parts".
There was a reason why in the 60's and 70's most promo shots of M4/M5's always showed the camera with a Summilux 50 f1,4 - it was the only lens that had "Wetzlar" on the front ring!