Group-- Having learned enough to know that I KNOW absolutely nothing, I was told that the screw in the back of the head tube was used to affix a racing number -- I presume on some kind of a plate or bracket that also "clamped" onto the top tube. There was one like it on a '59 Specialissima (sp?) for a friend. The older Schwinn Paramounts also used the integrated headset-- Cheers-- Nelson Miller in sunny Seattle.
I just bought an old frame on Sunday with the same kind of headset integrated into the head lugs as shown in the bottom picture for this 1958 Bianchi on eBay.
Mine also has another twist- a screw threaded into the backside of the head tube; looks like it was intended as some kind of lube port you unscrew to inject grease or oil.
Does anyone know how long Bianchi used this headset system? Any idea what the screwhole is intended for? Any guesses on the age of the frame?
Thanks. If anyone thinks pictures might help make the ID, I can take some digipix tonight and email them.
Sonoma County, CA