Mr. Potter is correct. On many American SxS barrels you can often see a braze line either on the flats or around the top extension joint area at the chambers face. I have only seen one Parker dolls head rib section come loose and it was also somewhat "held" in place or at least aligned with a vertical pin. Often times you can see this pin through the rib matting or it will be engraved on and around non-matted Parker ribs.
Channing
The doll's head rib extension is silver soldered on. I can attest to at least two that I know for sure were silver soldered. Two guns that "blew up"; one was the one Tom Armbrust, Sherman Bell and I (as an observer) blew up in the overload test. The other is a "long story" I won't go into. If the rib extension was soft soldered it would not add much strength. IMHO
