Norwood wrote: You should remember this is a bike made for the domestic Asian market. It's transportation, a means of getting around, likely the only means in most cases. Bicycles were necessities not recreational "toys" as we Americans now tend to think of them. As such the bike may very well be a pre-war design. Truely a "if it ain't broke don't fix it" attitude on Miyata's part.
'60's or '70's vintage seems about right for your bike.
I've been thinking the same thing Norwood, I'm also thinking that although it may be a rare bike here in the States, it's probably not so rare in Asia.
I'm still hopeful that someone can brake down the serial number.
Dave