RNV Hammerstop with lock in the grip frame
No overtravel of the hammer anymore. The RNV is easier to disassable and to assamble. Fits in the RNV grips with the lock. Mostly the serial numbers 510-xxxxx.
Threat of the screw is metric: M3
While this part is easily installed, it is not drop-in, it requires fitting by a competent Gunsmith.