Man is that nice! And I have a Scott 10 bore that could use some work like that. Yes indeed. But I haven't done damaascus (or double barrels). How much of that shine is oiling? The blued barrel above looks about as shiny but not like it is oiled.
I wish I has a decent picture of the 1877 Sharps I just did last week. I like it quite a bit, but it doesn't run with that blued barrel of your's above. I polish it to a much higher finish (usually 800) and then the luster drops to maybe 600 level finish due to the etching but I use a very dilute solution and low humidity. Still, it ain't like that blue double of your's.
The browning damascus seems like a whole different ball game and I'm still working on the simple rust blue method.
Brent