Yeah, they'd have to throw down some serious provenance to convince me that this is all the real thing. The question Robert.B implied above is an important one: would Doc have actually carried a knife like this? Perhaps if it was given to him by someone special to him, but it doesn't seem to match up with his persona all that well -- a fine ivory or pearl penknife I could see.
Yeah, I have to go along with that.
In his day, being a pro gambling man was a risky line of work. If you're any good, then 100% of your clients are going to be pissed at you by the end of the night. Either their will be sore losers for a poorly played game on their own part, or they accuse you of cheating and try to kill you. This is no time for obsolete tools like a percussion revolver.
People like the latest. In this case, by the late 1870's, the cartridge revolver was it. If they couldn't afford one, then the old cap and ball was converted. A lawman, outlaw, or gambler needed a good gun, and in a day when the metallic cartridge revolver was available to those on the edge, they'd have one or three around. Not to mention any little hide out pieces around.
I think it would be the same with knives. Being a gambler, there would be times when Doc was flush with money bulging in his pockets. He came from what I understand to be a genteel background, so I think he'd have something a little nicer than a shell handle pocket knife. Or maybe not. hard to tell with knives. But the field of western paraphenalia is one flooded with fake stuff.
It may his knife, or maybe not. I'd want iron clad providence.
But it is an interesting little knife anyways.
Carl.