Originally Posted by
realsteel
...If it says Hiduminium then you should be OK for the 1950's, not sure whether BM predated MiE though. I checked the Brown Brothers' Catalogues: there is no mention of GB stems in the 1938 and 1939 books, but the spearpoint stem features in 1952, 1954 and 1959...
My understanding has always been that GB was a post WWII venture.The brakes were reportedly introduced in 1945, then the bars and stems followed, circa 1948.