Rolf,
To date I have never seen a Kentucky style pistol with a spurred pommel & butt cap nail arrangement. There are pistols made in America that emulate the English horse pistol That have this same feature, but I don't count those as Kentucky pistols. Maybe there is an example out there I haven't seen yet. In Chandler & Wisker's book The Kentucky pistol there are three examples of spur pommeled pistols with what look like butt cap Nails. They are attributed to being made in America but I would not call them Kentucky pistols. I have seen a pair of original pistols that had silver butt caps held in place with silver nails vs a screw but the vast majority that have a but cap are held on by a single screw.