The link above refers to the 1994 catalog. Manually go to the miyatacatalogs.com site and look for the 1987 catalog. The 112 is there; it was called the 'top of the sport touring line.' The designation 'sport' meant their entry level bikes but even there the bikes have chro-moly frames and good components. Look for information about Miyata here, you'll find that they are a very well respected make. Miyata is exclusively a bicycle company, the oldest in Japan I think, and actually made the frames for a number of other brands. They even made the tubes in-house. Miyata is still a thriving business but dropped importing to the US when the yen/dollar balance changed in the 90s.

If in good shape that could be a very sweet bike---congratulations!