I believe that Bianchi started using that particular Campione del Mondo decal in late 1991, after they coaxed the Gatorade team of reigning world champion Gianni Bugno to switch from Moser to Bianchi. That would make it no earlier than a 1992 model, which is a pretty good fit with the mid-1990s estimate. That looks like a stamped seat lug and the BB shell is pretty basic. While is appears to be a Superest II version, it's certainly not the Superset II shell used on the high grade models during this era. This looks like a mid-1990s, mid-range model. Did you get the seat post size?