Right you are, Derrick.

There are some commercial trench guns in that serial number range, but this shotgun looks like a put-together. Among other things, it has a riot gun takedown lever and a late bayonet adaptor/heat shield.

And did anyone else notice that the action slide bar has the early style marking? I think by the time this shotgun was made they were marked "Model 97", not "Model 1897".