Not sure there is a way to tell. The dealer may be able to check the service record system and see if they show any work done to it? I will try to remember to look and see if we can tell the gear type through the view hole under the clutch basket.
I think there is: look at the VIN plate on the side of the steering column. My spare bike (an '86) is stamped Nov 85. So while it was sold and registered in '86, it was actually manufactured in November '85.
I'd bet early sales of the '85 were actually made in 1984.