No clue what the N number was. I lost most of my logbooks when my apartment was robbed a year or so ago which is why I don't give a hard number for my total time (somewhere between 500 and 600 hours, maybe 700 hours on the high end; all but about 100 was in ultralights). I've flown in so many aircraft- nearly every ultralight I've flown has been registered so that adds to the mix- that I can't recall the tail numbers for more than a handful of them.What was the "registration" you mentioned the 2-seat ultralight had you got dual instruction in if it was prior to the 2-seat exemption? The only legal registration it could have had was an "N" number prior to the instructor exemption.
I didn't realize that permutation of 103 was put into place so long ago but I probably should point out that my original instructor (in fact all of the instructors I knew back then) was a CFI. Not sure how that effects anything but it was a registered (N-numbered) ultralight and my instructor was qualified as previously mentioned so that might have overridden the "exemption" issue.As for your instruction and the other ultralight pilots you know that learned in the 1990s, it was undoubtably a 2-seat ultralight being used legally under the exemption. Part 103 went into effect October of 1982. The 2-seat exemption happened several months after that. There would have been no reason for an ultralight instructor to instruct illegally [with all the associated liability that entails] when the exemption was in existence.