Paratrooper,

If not for that scant stock, your rifle has many indications of being a USMC WWII rebuild. Something tells me the stock was added at a later date by someone other than the Corps. The serial number is in a range populated by many pre-WWI Corps rifles, and I have several known USMC rifles in that range with Sedgley 4-32 to 9-42 barrels.

For my money, it is a USMC rifle with a scant stock added by persons unknown. It is just an opinion.

Jim