There was one other bicycle manufacturer that utilized the under toptube seatpost clamp bolt if my memory serves me right, but I cannot recall the name off the top of my head. I would be pretty confident this would be a Legnano though. Looks like a very worthy restoration candidate. Those centerpull cable hangers made to attach to the back of the seattube are pretty hard to come by. I have a Legnano that was switched to sidepulls at some point before I got it, so that hanger is long gone. I've searched around for a replacement and come up dry.

Post photos when it's done!