I have been around some fine Damascus barrels, and they have a definite look. I cannot help but think that when these were made they did something to enhance the "Damascus" look to show off the fancy swirls in the metal. After all, during the transition time around 1900, some makers charged more for Damascus than fluid steel.
I agree that most of what folks are referring to here are really pattern welded "twist" barrels. The faux ones shown here could be mistaken on first glance for a worn twist barrel. It does make an attractive finish to my eye.
I know many cap lock muzzle loading shotguns were done with twist barrels. I have not seen an original period pattern welded rifled barrel to my knowledge. Has anyone else seen a pattern welded rifle barrel? I am guessing the increased pressure of a ball engaged with rifling makes a twist barrel less suitable for rifled than a smoothy shot barrel?
I can always use more knowledge! :-)
God Bless, Marc