The J2 was designed by
Drago Jovanovich and morphed into the H269 with Hughes and became the TH55/H269. If you believe the stories when he worked for Hughes he also had a hand in designing the H500 rotorhead
as well. Which if you look further you will notice that even the AH64 is only a fat version of the 500 head.
I was in El Segundo in the early 80's and went with a couple of guys to this small shop and was introduced to him as he was working on a tip jet powered OH6A.
The guys told me to go and have a look in a small cabinet in the corner and there was the prototype of the J2 H269 head and mast.
Interesting guy to talk to.