I belive these were made around 1990 - 1991 after the 400 series but just before the traditional series, I don't have any proof of this, its just a guess. It looks a lot like a 400 series. Does it have large xj frets or small vintage frets?
it has the fender style neck pocket instead of the esp style neck pocket that is cut at an angle and vintage frets is appears to be the same as a 400 series,
if you are comfortable taking the neck off there is a chance it will have some information in the neck pocket or on the heal of the neck. I personally think these are
very high quality, I have owned two 400 series strats, as well as a seymour duncan strat made by esp, and a vintage plus. They are better than any modern
production fender in my opinion. I have seen the 400 series strats labeled, 400 , 400 series, esp ( with no other information), series, and now vintage series. I don't
have any catalogs that old, so I can't verify any dates. These were made from the early 80's until 1991. I still suspect this to be from the end of that run. It Should
have all stock esp hardware, and esp pickups. Compared to other strat pickups I have used they are good quality.