winchester 1897 trench gun questions?

[Tom Doniphon]

The serial number dates it to 1918, not 1920. So it was made during WW1 and is in the serial number range of the WW1 trench guns.

But it has a WW2 type heat shield and stock. And the butt plate is a replacement, although it is of the type that the Military often used as a replacement.

I can't tell from your photos if the finish is original or not.

It's possible that it was rebuilt at Raritan Arsenal (the RA mark on the stock), but there's probably no way to know for certain.