This is the improvised gun made by Frank and later used by Earl (Jason Lee) and other characters during the failed attempt to break out of prison. It appear in the Episode #12 ("Early Release") from the third season.
Made with some random common parts smartly adapted to form a working firearm (a metal pipe, a door bolt, a broomstick, etc). This non firing hero version have the barrel soldered to the receiver and can't be opened. There is also a hole in the barrel to show that can not accept a load and will not fire a projectile.
Screenmatched in multiple scenes.
Always looking for Earl props. If you have something to trade or sale send a message!