Hello Peter, This is not meant to be an accurate definitive answer. Centre pulls have been round for donkeys years and like everything they keep on reappearing and getting reinvented. You can find very early bikes fitted with them and I mean early. Selbachs were fitted with CP's in the early 1930's. Like everything they are natural progression. The alloy types such as Burlite and the the other British makes were about in the 1940's, BSA made centrepulls before the war and Constrictor as well I believe, but these two companies were joined at the hip. Regarding Mafacs the first photo I think I can remember seeing was 1954 but I could be wrong. Wasn't Bobet one of the first to switch to Mafac's.
Thats all for now. Keep those wheels spinning, in your memories if not still on the road. Be lucky Mick Butler Huntingdon UK.