Correct Screwdriver:

[Bruce P Bruner]

Originally Posted by George Stanton

Do what you want but considering the high condition of that gun, I'd clean underneath that hammer without removing anything. It's possible you might damage something and that hammer is a wedge fit on the axle(?). Every time it gets removed and replaced the potential for it to get loose increases.

Sound advice for sure, best to leave well enough alone. “Do no harm” resonates with me. If it was broken internally it would require attention. Since it functions well it would be advisable to not take unnecessary risks.
Thank you George!

[Mike of the Mountain]

Just for future reference, the Brownells set and the extra thin blade set will handle most situations. Dan Rositter advised me to get a couple sets of the Grace hollow ground with the wooden handles. He said use one as is and if you need a special width driver to grind one from the second set on a drill press with a hard Dremel stone. It works slicker than goose dookie.