I picked up a Douglas barrel from a friend of mine, however, it was not stamped as mentioned. I know they are Douglas barrels because when they stopped making the muzzleloading barrels there was a batch put aside. The guy I got my barrel from is Wally Hart of R W Hart and Sons. They specialize in making high power rifles that perform in the super shoot sports across the country. He swapped out some of his stuff for the remaining barrels and they were only had in 45 or 54. I got a 54 and built a rifle from it. Damn thing shoots great! The reason, as I understand it, that Douglas stopped making BP barrels is because they were using 12L14 steel. This steel has lead in it and can burst. They were deemed unsafe and there is much discussion today in regards to that. Anything can burst if not properly cared for....balls halfway down, overloading, using SMOKELESS powder, double balling, extreme heavy charges, barrel obstructions....you name it and it can happen. They are good barrels and they saftey factor concerning them is (in my opinion) bull puckey. If those barrels were SOooooo unsafe, then we would see many, many, many injuries and a daily basis...just think how many of these barrels are out there....there are countless thousands, yet it doesn't occur. There are shoots held every weekend across the USA and as far as I know, there have been no barrels burst that have been the dreaded 12L14 steel.
You got a good barrel, if it is a Douglas. You may want to check the twist to see how fast it is...good luck with the project.