Jerry, that number points to it being built in March 1950 50=1950 3 =
March. 418 = total bikes built that year. When they reached October the
sequence went back to zero = 0 for the tenth month then 1 and 2 for November
and December. The large lower number would then indicate which was the
latter months. I cant ID the model from this, only the lug style and
configuration. Hope this helps.
Mark Stevens Dingwall Scotland.