Is there a reference that lists when changes in specification occured on the M20 in relation to serial numbers? Items such as sidecar lugs, tank styles, fenders, carriers, and seat sprigs come to mind, as things that changed over the war years. I have both the BSA Singles and Twins restoration books, which give a pretty clear idea when changes to specification were made.
There is a great volume of knowledge here on the forum, is there an M20 Buyer's guide that shows the evolution of the M20?
Vince
