Not sure... It should be too old to be a KO, but it is still possible.
I'm sure there are telltale signs as with most KO's, but I don't know what to look for unfortunately.
Comparisons to my G1 Prime I got for Christmas in 1984 (or was that '85 ?) are identical. Nothing looks like it is made out of "cheaper" plastics, stickers are a perfect repro if not genuine etc...
It could also be a genuine Prime with a KO sticker as well. Maybe I'm better off not knowing, keeping the dream alive...!