Maybe you all know this but
here at vintage-trek.com is a lot of information about dating components, many of which are Asian. (Information, and/or misinformation. I have no idea, though I'm sure it's all well-intentioned.
Incidentally, I have a Suntour front derailleur that looks newish by Suntour standards and is stamped "JD". The "J" takes it just off the scale explained in that web page, but by extrapolation it would be 1993, which seems reasonable to me. (
Suntour's history is rather confusing.)