I'm with Mike, I hadn't thought of it but the trench gun was purpose built for WWI and 1908 rules that out. I don't think any 97s were military until WWI.
I think i have a converted nickeled M97 riot gun that would be worth about twice as much if it was unconverted and original blue.
Cool gun though. If you've never handled a 97 it makes you realize what a marvelous gun it was to be, in the case of the one I have 102 years old. Slick and fast. Hammer falls when you hold the trigger down.