[fernando]

Jim, perhaps a significant fixing method other than the screws entering the cup from the outside and meet (say) the pas d'ane, is the one in that the cup is welded to the quillons. I assume such system is more seen in Portuguese swords, but nevertheless to be taken into account.
Currently, from the four cup hilts i have hanging in my wall, three have the cups welded to the quillons. Not counting with equal number in my archives, which i timely deaccessed.
Rings in locks of firearms are completely a different business. While fixing screws in sword cups serve basically on a permanent basis (except for sporadic maintenance ?), those in (flint) gun locks are more handy that vented head screws and serve to often unscrew to change the flint, whether worn or broken.

.