I bought the MarkIV in '96. I was told that it had been in inventory at the music store for just over a year when I got it (the asst. mgr was our drummer at the time and suggested this amp when I was ready to move up to the big time). So it might be the same year as yours, or real close. I don't have the s/n handy or I'd post that for comparison.
The Princeton may not be a boost, but it's a really cool piece in it's own right. I snagged it from my dad (I'm 42) who used it to amplify his 69 Martin D-35 in church. I'm not sure when he bought it, I never thought to ask. It is one of the first 400 made and is original aside from a repop footswitch, tubes, a few caps, and a grounded power cords so I can actually play it. It sounds awesome by itself and killer put through the EV Thiele cab (the 1x12 EV-loaded 3/4 open back cab that it's sitting on in the photo isn't a good match for it).
Thanks for your comments! -Dave.