Re: Old shot gun
The name "Long Tom" for any long barrelled gun or cannon goes back centuries; the best known today is probably the 155mm gun used by the US in WWII, but the 280mm "Atomic Cannon" was also sometimes called the Long Tom.
So the makers or sellers of that shotgun didn't invent the name, they just used it. The shotguns given that name were utilitarian guns and are of only modest value today, usually around $100 if in good condtion, which few are. I strongly recommend against firing those old guns with modern ammunition, and some should not be fired with any ammunition, even black powder shells.