The hole that rests screw into was originally there for Burger Buttons (cushion plungers). I still have one from 1985 or so with a Golden Key arm rest.





Buttoni.e. Plunger, Burger Button—The button is a device that, when the arrow is being shot, prevents the rear of the arrow from overtaking the front. It also aligns the arrow in the center of the bow and keeps it from hitting the bow once shot.