It's at least a 1987. The components may be from late 1986 but 105 SIS was introduced for the 1987 model year. Bicycles sporting Shimano 105 are typically considered low, mid-range models. Tange Infinity is a seamed, CrMo, butted tubeset, while the Mangalloy forks (and almost certainly stays) are a carbon-manganese alloy that was used as a cost cutting measure over CrMo. It's not quite as strong as CrMo and therefore is usually a bit thicker to compensate. It is therefore heavier, though not as heavy hi-tensile steel.

From what I can see, it is all original, with the exception of the period correect Look PP66 pedals replacing the original Shimano 105. The paint scheme is a typical late 1980s, pastel fade, courtesy of the influence of the Miami Vice TV show. Original price in 1987 was $480 US.

Please proivde the serial number for my database. TIA.