I have no idea on this but always assumed it was just a progressive numbering system employed by the Cinelli works . Way back in the dark ages in 1952 Cinelli numbered their light steel handlebar range as M.11 through to M.14. M.11 SanRemo M.12 Gran Fondo M.13 Giro D'Italia M.14 Pista M.15 Koblet M.16 Tour de France. Athough the steel extensions were refered to as Road Racing and Sacchi (track). No 1a back then.