Put a Back To The Future 3 Reference in
The end of the episode, where Sam receives a package from Samuel Colt, is a direct reference to the end of [http://en.wikipedia.org/wiki/Back_to_the_Future_Part_II back to The Future Part 2]. At the end of the movie, a courier from Western Union arrives minutes after Doc brown has disappeared in the DeLorean after being struck by lightening. He gives Marty a letter, sent 70 years ago, with instructions for it to be delivered at that exact day and time. It is from Doc, who has been trapped in 1885 after the lightning strike caused the DeLorean to malfunction.
There is a probable reference about "Daniel Elkins" and how he got the "colt".When Sam told Dean to get the ashes of the "Phoenix" he threw the colt and started to run.The gun fight happened near the Saloon which is owned to someone named Elkins.Elkins probably was a hunter and he watched the duel.After there is no one left in the area he took the gun and kept it for himself.So gun finally passed to his grand grand grand son "Daniel Elkins".