Check and see if it says Dumoulin 8 C instead of what you had as "Duiaoulin"?
If it is Dumoulin 8 C ? Your shotgun was made in Belgium by Henry Dumoulin company. They were hand made shotguns and very high quality for the time. I am not sure of all of the history but Henry the father built shotguns from around 1894 to 1930. His son Earnest took over the company in 1930.
We would love to see a picture of your shotgun if you could post it for us. We could maybe take a closer look to confirm the above. The DAMAS and the brown swirl design you speak of assures it is probably a Damascus Barrel which means you should not shoot modern shot shells out of it. The Damascus Barrels were designed in a day when they were using black powder and not progressive powder. It is a very fine shotgun. And what is its condition?