Royal Damascus was a mark used by Ancien Etablisment Pieper of Herstal, Belgium, c. 1890-1914. T Barker is usually dismissed as "just another Belgian clunker", but with a silver escution and engraving, yours is probably better than the average utility shotgun from the period. I have heard that T Barker was a hardware outlet in California, but have no proof of that.
Simonis, Janssen & Dumoulin, c. 1884-1905, in Belgium
A couple hundred dollars.
10-100 usd
700.00 dollars
50 bucks in good condition
No.
Most likely was imported from Belgium c. 1900-1910. "Nitro" refers to smokeless powder, so it would have been made after 1900. Damascus barrels would place it before WWI.
No published history on the company.
Your gun was made by the Dumoulin firm in Belgium between 1885 and 1905. Value will be under $250.
A damascus barrel is a barrel made of damascus steel, which is steel produced by hammering two different steels together. The twist refers to the pieces of steel being twisted while they are hammered, which produces the distinctive pattern on the steel.
Damascus barrel (in French).
Not.