Bianchi was not the only company to use integral headset/lugs, which go back at least 100 years.
See the vintage velos museum bike 1935 Umberto Dei:
http://vintagevelos.com/
Bianchi used the integral headset/lugs until at least the late 1960s. If your lugs look like the ones on eBay, your's could be anything from about 1946 until about 1970... if they have a notch in the side, they are mid 1940s or earlier.
See a 1920s Bianchi:
http://albums.photopoint.com/
and a mid 1930s Bianchi with notched headlugs:
http://albums.photopoint.com/
and a 1940 Bianchi, also with notches:
http://albums.photopoint.com/
and vintage velo's museum bike, 1949 Bianchi:
http://vintagevelos.com/
As for the screw in the back of the headtube, it makes more sence that would be for grease injection. What kind of racing number would you screw onto the back of the headtube???
Aldo Ross
sunny, warmer Miltonville, Ohio
> 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.
>
> http://ebay.com/
>
> 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.
>
> Bill Mattinson
> Sonoma County, CA