TKs for posting those pictures, Doug. This is the gun that 'Middlesex' in the States and Heritage in Ontario sells. The breech, with the 'plate' ahead of the tang is identical and found only on these 'Indian' guns as best I know. The one I had for a brief period of time, had only 4 threads bearing (engaging) inside the barrel's breech end, one held by .002", one by .015" and one at .022" and one at .028". The rest were smaller than the threads of the barrel. The plate's pressure against the rear face of the barrel is what kept the powder gasses from blowing out around that joint. Due to the thickness of the plate, and the gouge around the plug immediately in fornt of the plat, 3 and possibly 4 threads were missing.
I was shocked and returned it - which they refunded - thankfully. I also took a whack of pictures of the barrel, plug, etc, but have not uploaded them to photobucket - yet. I'd rather not.