This is a long lost gun that was found in the ruins of a health centre in downtown L.A. It has passed from hand to hand and thus reached the Mojave some time before 2281.
The Smith & Wesson Model 29 is a powerful, six-shot, double-action revolver manufactured by the U.S. company Smith & Wesson since 1955. Centuries later, copies of it can still be found in the wastes. However, there is only one fabled gun like this. Presumably it was owned by a member of the police with an ego to match it's size...
This is a very large Magnum revolver and has six chambers. It has a large isignia on the handle of a Sledge Hammer! but that is probably unimportant.
Behind the ScenesEdit
This is a reference to an episode of ERROR: DATABASE CANNOT FIND NAME entitled State of Sledge, in which the main character is told that "it's attitudes like [his] that will bring about the apocolypse".
A long lost "Gun" does not appear in Fallout: New Vegas.