Hi Ron,
The 2 marks with crowns are the London Gunmaker's Guild view and final proof marks. It is not "CP" but "GP". The style of deep stamped oval predates 1813. It indicates the barrel was London proofed not at the Tower or in Birmingham. The barrel is stamped with Richard Wilson's mark, which was used by his son well after he died in 1766. The "LG" may be an "IG". I cannot see it clearly in the photos. The barrel could be made in Birmingham but proofed in London by Wilson. It appears to be a common trade gun style barrel. Superficially, the wood does not look like walnut but possibly maple. The mix of the iron guard and the other brass hardware strongly suggests to me a restocked gun possible in America after the Rev War. The style of the stock seems later than colonial America and much more late 18th, early 19th century.
dave