it has some character for sure, the light grey finish on the USMC is from them not cleaning and refreshing the tanks as much, the markings on the barrel are from a plumbers table, like a 3 legged table with jaws and what not to thread pipe, the stock is a mystery for sure, looks for sure someone has played with the grasping grooves,
every USMC rifle iv seen has had a hatcher hole, stippled buttplate, serialed bolt, and a few other things that add them up to Marine use. other then if it hit on SRS, its hard to say for sure