The Undead Cowboy outfit appears to be the bloodstained remnant undergarments of the Elegant Suit, minus Marston's hat and dark suit jacket, along with a ragged red headband, similar to the one John sports in promotional artworks for Undead Nightmare. It also features a bandolier over Marston's shoulder.
It replaces Marston's standard Cowboy Outfit after the completion of Undead Nightmare's story mode. Similar to its counterpart, the Undead Cowboy outfit offers no in-game bonuses and benefits, aside from the reduced attention Marston will be given by Undead creatures, though this applies to all outfits after the completion of Undead Nightmare.
The Undead Cowboy outfit is unlocked following the mission"On A Pale Horse" and the completion of the story mode of Undead Nightmare.
In the main boxart of Red Dead Redemption and several promotional artworks, John wears what appears to be a clean version of the Undead Cowboy outfit.
The condition in which John dies in the Undead Nightmare timeline appears to be different than in Red Dead Redemption; John was buried in his Rancher Outfit after being shot numerous times in his body, whereas in Undead Nightmare John was buried in his Elegant Suit.
Several trailers for Undead Nightmare featured an undead Marston with what appears to be the Reyes' Rebels outfit instead.
The Undead Cowboy Outfit is the only outfit to feature the bandolier once the main story has been completed.
Despite the Undead's primary weakness being damage/destruction to the brain, Marston appears to have suffered a gunshot to the forehead. It is unknown as to when this wound was sustained, as the original game does not include him being shot in the head.
A pre-release version of the Undead Cowboy discovered by Twitter user Winchester1899 shows the outfit was originally Marston's regular cowboy outfit blood soaked and torn in a similar manner to the final Undead Cowboy. Marston is also shown to have eyes intact, no headshot wound, and his mouth was soaked in blood similar in shape to the final version which has rotted away.
In unpatched versions of Undead Nightmare, the artwork for this version appears instead of the current version.
When John becomes undead, he is less resistant to explosions from both Retchers and the Explosive Rifle.
Promotional artwork depicting an undead John wearing the outfit.
In-game menu page for the Undead Cowboy outfit.
Close-up of undead Marston wearing the outfit.
The outfit's multiplayer counterpart in the Outfitter.