Originally Posted by rickystl
...The three screw lock seemed to be dominate on early guns/locks - of English manufacture. But it's not a hard fast rule...
You are right; this system has also been an option in this side of the canal.
This blunderbuss i locally acquired the other day has such lock fixation method. Also we can see in works like ESPINGARDA PERFEYTA that, the three screw system was used over here as early as from the XVI century. Perhaps early locksmiths saw it as a need to better fix lengthier plates, the Portuguese "molinhas", being a good example .