Originally Posted by mindfrieze
The seatpost diameter is 26.8 mm, and the B/B shell width is 68 mm with standard ISO threading.
Those point toward a Japanese frame, the last clue might be if you ever get the headset off this to see if the fork crown is a 27.0 (JIS) diameter, that would clinch it. So this might be a "missing link" between Ital- and Uni-vegas. It still could be the work of Miyata, but I wonder if anybody has ever seen another branded bike with these lugs and other details?