Belgium is the country of origin, not a brand. Innumerable old damascus barreled shotguns were made in Belgium and imported into the US before and after the turn of the century. These were generally low cost shotguns, of no current collector value (better guns identify the manufacturer). If the Damascus pattern is pretty, and the receiver still has case colors, it may have some value as a wall hanger. DO NOT ATTEMPT TO FIRE IT! Damascus steel cannot withstand the pressures of modern smokeless powder. Even black powder should not be used unless the gun is fully examined by a very competent gunsmith.
No. What would the company that produced the finest American double barrel shotgun want with a utilitarian import?
Simonis, Janssen & Dumoulin, c. 1884-1905, in Belgium
WILMONT GUN CO guns were made in Belgium from c.1880 to c.1915. Value is going to be low, with excellent examples under $400. Please do not attempt to fire the shotgun.
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.
The value of a Simmons Royal 16 gauge double barrel shotgun depends on a number of factors. Most important being the age and condition of the shotgun.
Royal Observatory of Belgium was created in 1834.
ROYAL STEEL was the marking that indicated the barrels were of fluid steel rather than Damascus. LC Smith introduced Royal Steel as an option on the F Grade in 1917 and by 1919 only Royal Steel was available on all grades.
The value of a Simmons Royal double-barrel 12 gauge shotgun varies by its condition. As of 2014 this firearm in excellent condition sell for around 150.00.
Enders Royal Service shotguns were distributed by HD Folsom to the hardware trade from c.1890-1920. They were imported from Belgium (will have proofmarks) and made domestically by at least two different manufacturers.
Depending on the condition of the firearm. It could fetch as much as one hundred seventy five dollars in great shape, or as little as fifty dollars in poor condition.
Wiliam Moore was an English gunmaker, 1854-1872. Foreign copyrights weren't too well enforced in those days, so Henri Pieper of Liege, Belgium, 1877-1898, borrowed his name for inexpensive shotguns made for the American market. Value is about $150-$250, depending on how well it looks over the mantle. Damascus barrels over 100 years old shouldn't be fired unless they have been approved by a competent gunsmith, and then only with the black powder equivalent loads they were designed for.
There is a long list of shotguns that are marked Royal, but I cannot find the United Arms part of your marking in my lists. All that I do find are attributed to Anciens Etablissments Pieper in Leige, Belgium, so I would bet on that being the source of yours, too. Since this version of the company name was first used in 1905 and the export of civilian firearms from Belgium ended when the Germans invaded in 1914, that would make your gun right around 100 years old.