In the one I have, the cross pin keeps the valve from being pushed back toward the hammer, and there is a valve retainer screw, which also acts as the front frame screw mounting point. My NPT plug does not interfere with the valve removal, though I suspect that a standard fitting *might* screw in far enough to cause issues.
Brass Monkey Customs I am not longer accepting work. Sorry. I do not have any tubing for sale, nor will I be restocking. Once more, sorry.
My feedback: MCB