I have three antique Pacific and Bair "C" presses with the primer arms mounted in front of the ram on the bottom, and they all have a slot in the top front where the dies are mounted for a primer feed system. In the side of the slot is a hole for a 1/4" x 28 threads per inch screw/bolt or what to mount this primer feed system? Does anybody know what the configuration of this screw/bolt was in the original issued Pacific primer feed set? Was it a plain screw with a flat screwdriver head? Or maybe a set screw that took an Allen wrench? Or maybe a larger screw with a ribbed knob with an Allen Wrench hole in the end? Or maybe even a regular machine bolt that took a hex or socket wrench?