Originally Posted by T-Mar
As John E states it's a Japanese made Bianchi. As USAZorro's analysis of the seat tube decal confirms, it's no earlier than 1987. Bianchi won the World Pro Road Championship again in 1992, so presumibly the frame fits into the 1987-1992 timeframe. Tange Inifinity was a seamed CrMO tubeset, which in conjunction with the Japanese manufacture, would probably make it a lower, midrange model. Is there a model name on the top tube?
Checked it over, there doesn't seem to be a decal on the top tube, nor is there any evidence there ever was one. If it helps one of the things that annoyed me was the cable stop for the chainstay is mounted on top rather than below so I can't use the plastic bottom bracket cable guide. Evidently my frame also did not come predrilled for one, nor were there braze ons for cable guides.