Great comments and ideas on identifying this but here’s a comment from my buddy Ken Hackathorn so I’m going with this 👍🏼
“Yea, I remember them from the distant past. Was supposed to allow the user to dial in the
vectored recoil impulse to control muzzle rise for either right or left hand users. Pretty much
a joke, like so much of the gun world gadgets…it faded pretty fast.”