This is my 1948 BSA M21 YM frame number despatched 22nd June 1948 matching numbers, so I assume one of the last of the Girder/rigid M series BSA,s. 1949 M series should have a ZM frame number and as far as I know had tele forks, I had a 1950 ZM with tele,s never seen a ZM front frame with the long front down tube for girders though ? Dave
