Looking over the Miyata catalogs it appears that they expanded the line at the 'low middle' as that was probably a hot price point. So they had the 100, then the slightly better 110, then the even-better-but-not-yet-a-210 112, and on the other end the 90, then some bikes below that. As the years went on a certain model tended to get better specs but not always. I had thought my daughter's 100 was a 1986, but the paint (silver on the front tube) shows it to be a 1987, which means the fork is hi-ten rather than mangalight!