they may have started making mustangs ealier than they did jaguars. there's this mega famous artist over in japan, and he just happened to use a mustang. i think it's the case that you can walk into a shop in japan, and it's pretty much a load of mustangs in one corner. and i think the japanese mustang production starting year was 1983. i suppose it could also have been the same for jaguars. but 1985 is the year that seems to be banded about.
also, i think it would be useful to find out when fender of japan actually came into existence. the first japanese fenders were really the squiers, made in the very early 80's. all strats etc, none of them jaguars or mustangs. if squier were formed in '81, then when did japanese fender guitars actually start saying "fender" on the headstock?
you are right, 80's jaguars seem rare. i know ones that were made around '87 would be the "E series", with a red A surrounded by a circle stamped on the butt of the neck. it's also possible that none of these jaguars really made it outside of japan. were never officially exported to the USA, or anywhere else. and that, in the 90's, when people started seeing sonic youth and nirvana, there were official periods of exportation. in the same way that just as today, we get the 2003 LPB and CAR jags/jazzies without matching headstock. or the current black jaguar specials.
nowadays of course, we have the internet. so it's easy to find out (or at least try and find out) what fender of japan are actually making. rather than back then, when you'd only see what fender wanted you see was coming out of japan, and it was almost a secret shrouded in mystery