Back when I refurbished around 1980 (with your assistance, juvela ) we "knew " what kind of bike it was so, no investigation needed. I haven't taken it apart yet, to look at steerer.
The HS locknut has CAMPAGNOLO---PATENT---CAMPAGNOLO--- ITALY---

Frame is 56cm center to top.

I am pretty sure about the BB threading, because he took out the Campy BB and replaced with Phil Wood, and I have an Italian Campy BB in my stash, and don't know where else it would have come from. Looked all over the seat tube, don't see anything. Paint is pretty thick, and lots of touchups.

I replaced the adjusters back then.

Thanks again, glad you chimed in.