Geraint, Thanks very much for the input! I'm of the same opinion that regardless of original or not, the stock has been refinished. It really reminds me of the kind of finish most Mosin Nagant rifles got after the war, a kind of patchy shellack look to it. The pan cover appears to be the same metal as the rest of the pan.
The barrel protector is indeed brass (if you mean the band just forward of the pan wrapping the barrel and stock) and is somewhat loose. The pan has been fired (the gentleman I bought it from has confirmed that he had been shooting this previously) and the match holder shows signs of patina from firing as well.
One of the first things I did when I was looking at buying it was to compare it to the dixie gunworks reproduction as the previous owner didn't know if it was an original or reproduction either and I came to the same conclusion that it doesn't appear to be that particular one if it is indeed a reproduction. I don't know of any other companies that ever made them, which is why it then felt to me like it could have possibly been an original. That said, it could also have been a custom build from a parts kit or from the dixie kit but modified. Entirely unsure.
Even if it does turn out to be a reproduction, I'm still thrilled with it as I got it for a steal being as Dixie was selling them for over a grand.
The barrel inside diameter is 12.25mm on my digital calipers