Serial numbers:

Here's what I've read on the web:

Miyata serial numbers are usually found on or near the bottom bracket. The initial letter indicates the year of manufacture, starting in 1972, so:

A–1972, B–1973, C–1974, D–1975, E–1976, F–1977, G–1978, H–1979, I–1980, J–1981, K–1982, L–1983, M–1984, N–1985, O–1986, P–1987, Q–1998, R–1989, S–1990, T–1991, U–1992, V–1993, W–1994, X–1995, Y–1996, Z–1997. Some frames would have been manufactured in the year before their model year, so, for example, a 1986 model may have 1985 serial number.

Beginning in the late '80's some Miyatas were made in Taiwan under contract with the Dod Sun firm. These have a 2 line serial number, beginning with DS. My understanding is the the next figure is a digit indicating the year of manufacture, where an 8, for example, indicates 1988. I don't know how the years from 1990 and beyond were indicated.