I will guess very, very early 1989 based upon a couple other serial prefixes that I am aware of. In the mean time, there's a couple bits I can see that you may or may not be aware of.
First, I agree --condition is just fantastic. If you also have the box with intact end label, that can get us a pretty close date but definitely e-mail S&W as suggested and when you hear back from them, please update this thread!
You probably realize this, but the pistol is wearing an aftermarket Hogue rubber grip. It was shipped with the very early one-piece grip and that grip was likely subject to recall. It would not be difficult to find a proper grip for it if you wanted to bring it back to (close to) original.
Yours is an extremely early 4506, and an early 3rd Gen. The slide on these was actually older stock that S&W used up and modified before making a new run of slides that look a bit different. There are easy visual clues to this. The rear sight is a fixed blade when nearly all the fixed sight 4506 pistols got the Novak lo-mount sight.
Another clue that the slide was an upgraded 2nd Gen is the older style font for the long Smith & Wesson lettering and especially the old style "four lines" of information located right over the slide stop.