Originally Posted by Oldairhead

I have 4 Girardengo's and none of them have the Ser. # on the head tube or lug. I believe that those numbered as shown above were likely made by RIH and were perhaps the top tier models. Interestingly the different head tube badges offer one of the few clues to dating a Girardengo, the upper one being pre-1958 and the lower one being post-1958 according to most accounts.