The rear brake bridge looks the same as those on my Columbus tubed Massi and Viner frames, which are from the late '79's early '90's but the fork crown and steerer and pump pegs indicate an earlier build. Do the brake bridge and fork crown accept a recessed Allen key brake mounting bolt, or are they parallel all the way through, to accept nut-on fitting brakes? This would help to date it roughly. In any event, it looks like a quality frame and Italian in style - although it could easily be a "Belgian Italian", hand built under licence in Northern Belgium. This could explain the apparent anomalies. An interesting find.