I'm not too familiar with the 'early' version of the M20 with the 3 bearing crank etc....It is clear there were a few prototypes in 1936/37 but were any more produced after acceptance in 1936, but before the models with the revised engines?...If so what would the frame and engine number prefixes have been?....Also, does anyone have a precise date for the introduction of the first, more familiar revised types that superceded the early bikes?....Ian
