Max,
Like many things Randall, some things were done (and often) before they appeared in the catalog. Most certainly this knife could have been made in 1984 but a knurled handle and lined butt cap could have been made before that time. Many, many, many of these knife handle/butt cap combos would not interchange, back in the day. I have no idea exactly "why" but threaded butt caps would often burr-up and strip when they were tried on another handle. I guess the cutting tools would wear, etc. This doesn't seem to be the case nowadays.
I only mention this because many RMKs fall victim to "1st in- last out" when it comes to things like sheaths and compasses...not so much with these butt caps during this time period.
Best, Capt. Chris