I think Bailey is right. Wild Bill carried such a variety of firearms at one time or another, it would be hard to say exactly what he carried them in...One thing I have read (somewhere) is that he carried his Navies in a sash in town, but on horseback, he used reverse cavalry draw type "slim-jim' holsters...but to me, I can't help but wonder just how this info was established.
Costuming and so forth on DeadWood seems overall, pretty accurate and at this point I have to say I think those who are responsible for it are doing a pretty good job, given the constraints of no one today was alive back then to check them on it...I'm a big fan of the show, ( could use a change in the language though. Been enough f--ks for a show that ran 10 season just in the first season)