some facts about Dead Man's Gun (contains spoilers)
type of gun: Smith & Wesson Schoefield
caliber: .45
letters: Se(sometimes confused as Sc)
meaning of letters : Sepilare(sp) ac Eradicae(sp) which are latin for Ruin and Destroy( this was revealed in the season 1 episode "Next of Kin" )
Owner of gun: Mr. Smith aka The Grim Reaper (series finale "A Just Reward'),played by Kavan Smith (you'd think they would have Kris Kristofferson play that role, oh well).