I've been scratching my head over this one, comparing the frame details to all the catalog years and wondering if it could be anything other than a 1989 1100a? (model number is nowhere to be found on the frame)
Miyata Alumitech - Imgur
The strange thing is that the serial on the BB starts with "SU..." which I think would indicate it was made in 1990.
Any thoughts or musings welcome and appreciated--thanks fellow Miyata lovers!