As it happens, I have both the Nishiki East Hill posted, and the one that phoebeisis posted. Same colors and logos and everything. Both of mine came from the sellers with aluminum rims, etc. The pink one has a date stamp (can't remember where, bottom bracket probably) that dated it as a 1984, and the burgundy one was sold to me by the original owner as a 1986. The burgundy frame lacks a lot of the nicer details that were on the pink one -- some things that were lugged on the pink one were not lugged on the later model, the workmanship is just not quite as nice, etc. -- but the components were slightly nicer (particularly the crankset). So I tend to believe those dates.

I wonder if someone just swapped out some older components onto your bike? Or hopefully yours IS older, because frankly the 1986 Sport is kind of a piece of crap. I was really disappointed in a side-by-side comparison of it to the pink one, which I've converted to a single speed and which is my favorite bicycle out of any I've ever owned. I haven't even bothered to rehab the burgundy one because I'm so disappointed in the frame, and at this point I will probably just use it for parts and then give the frame away.