This is actually a modern flintlock with Faux Damascus
An late Ottoman miquelet with Faux Damascus
Another Ottoman miquelet with damascene, engraving, again Faux Damascus.
Yes some have "blackened" or blued Damascus to hide it. Originally it was normal to find "black & white", blackened, "brown & white" or browned. Puraye talks about all 4 methods. It was also possible to see barrels that had been etched in hydrochloric acid. A finish sometimes preferred on German guns.
You can see original samples of these finishes here:
http://damascus-barrels.com/Finish_Restore.htmlDamascus barrels straight off the forge will not show any pattern. I have some here waiting to be ground. The barrels have to be ground then struck. This removes the surface material from the hammer forging and exposes the layers of the billets. This was done during the grinding. The striking enhances the pattern. I believe Dr Gaddy used to recommend 300 or 350 grit before the etch.