[TARNATION !!!]

Some pics to let you see the parts involved. Patience is a virtue for any work on an old gun. Good penetrating oil soak for a good bit of time first. Then clean the screw head slot with a toothpick until you get all the "crud" out. Then a hollow ground turn screw bit that completely fills the slot. Then downward hand pressure while keeping the bit firmly against the bottom of the slot and begin to exert counter-clockwise pressure - start gently. If it won't budge, let it soak longer and try again. You should eventually win without marring the screw head. Once the parts are out, clean them completely and work the rod with steel wool. I run a .22 cleaning brush through the hole for the rod to clean whatever might be in there. Some gun grease on the rod and slide it back and forth a few times should do it. If all is good, finger pressure should move the rod. I also disassemble and clean the cocking hook parts.

Of course, you can never go wrong by sending your gun to a pro to perform this type of maintenance. Cheers, Jack