I never figured out a year for mine either, I have a sense it is late in the production run (80's). The owner's manual has a note listing as a 1992 which is not possible. I can't find a VIN
on the frame, the number that was once upon a time embossed in the shell was not readable when I got the trailer and the plate with the specs riveted to the side has been stamped 92.
Hope you figure it out, maybe someday I will figure mine out. As for the government they are just fine with a registration
listing it as a 1992, so what the heck...