I stumbled across a video on the John Pedersen designed Remington Model 10 pump shotgun. The model featured in the video was the trench shotgun made for the American Expeditionary Force in WWI. Remington made approximately 3,500 of these shotguns equipped with a 23-inch barrel, a bayonet lug, and a wooden handguard or heat shield on top of the barrel. This shotgun was the lesser known trench gun used in that war. The Winchester Model 1897 was the shotgun that is more widely thought of when you say trench gun.
A copy of the original owner’s manual for the civilian version of the Model 10 is here. While only 3,500 of the military trench guns were made, Remington made approximately 275,000 of these shotguns from 1908 until 1929.
What makes this shotgun so interesting in my opinion is that it is a bottom ejecting shotgun like the more well-known Ithaca Model 37 or the Browning BPS. That combined with a simple, Garand-style safety, and you have a shotgun that can be used by everyone regardless of dominant hand. Add the long “pig sticker” bayonet and you have a very potent and deadly firearm for defending or attaching trenches.
Given that so few of these shotguns were made as trench shotguns and given that many of those were converted to riot guns, I’d hesitate to say what one of these would be worth nowadays except to say “a lot”.