Thanks for taking the time to reply.

Actually I immediately called the Dallas gun room and a nice gentleman (who I could barely understand)took the time to look up my gun and read it to me. There was no mention of the caliber at all, which seemed to puzzle him. It did mention the left handed stock, the long top tang and sling swivels but not much other of value.

I then wrote to the London office thinking they might actually have a historian who might know something about the history of these old guns. I got back, (after several weeks) a reply basically telling me to bugger off, they had no time to help.

Purchased with the rifle was 20 rounds loaded (by Ken Owen in 2011) with Woodleigh 440gr bullets at ~1650 fps.(54gr 4198 with wad) These loads put one left and one right shot 2.5" apart 2" above the point of aim. Not too bad but not as good as my loads.

The chambers were measured, by me, at 3" long. The bores measure ~.507" for the left barrel and ~.509" for the right barrel, both at the muzzle. Both barrels have some fouling which might be effecting the measurements. Neither barrel seems to have been touched by a cleaning patch since new! I'm working on that also.

No pictures right now but I'll work on that.

No one can venture a reason for the large "S" included with the proof marks?