I am a nerd. There, I said it.
I have figured out, thanks to the nerdery afforded me by this board (and my bordering on OCD passion for knowing labels proofs, ages and whatnot,) that if you were to watch Deadwood and key in on the bottles always being consumed by Al Swearingen and the people at the bar at the Gem Saloon, you'll see that they are consistently drinking from Old Weller Antique labeled bottles. I'm pretty much 100% certain at this point, as I've watched 12 episodes in 3 days.
If you think about it, it's a very smart choice, as it looks old-timey, and you can catch glimpses of the number 7 on the sides for the age statement. Pretty much any time Al pours a drink either at his bar or in his room while consulting with people, you'll see the OWA label.
Someone mentioned awhile ago that Bulleitt bottles show up, and that's also true in one particular scene around a campfire in the town, but that's the only scene I've seen it in so far...I've also seen one old label for Old Overholt in one scene as well....but the dominant one they went for is OWA.
Totally random, unnecessary knowledge, but hey, this is SB......thought it was interesting. If nothing else, maybe this thread gets you to revisit how awesome Deadwood is and you can have some OWA yourself while you see if I'm right or wrong.