It looks like some sort of four-bladed flybar, but why would you need this on a rigid rotor?
Stability? Rigid rotors with large hinge offsets are not exactly the most stable.
And the 117 grew like Topsy from the 105 so..............
Maybe an attempt to get rid of the electronic SAS?
Look up the Lockheed Cheyenne and see how well that flew with a Rigid Rotor and a Stab bar. Youtube has some pretty good movies about it. Impressive.
I am guessing that when they did the "stress analysis" on the Cheyenne though they probably crapped themselves or back then didn't know enough to be concerned!