I agree with Merc. Barring any as yet unmentioned defect, $450 sounds like an excellent price and the rifle in question sounds like a good "representative example".
For years, I've heard stories about WWI "cleaning parties" where soldiers would strip their rifles and toss all of the smaller parts into a communal pot of solvent. As the story goes, after cleaning the parts they'd reassemble their rifles without regard to which part came from which rifle. No idea how true this is, but in my experience truly original Model of 1917 rifles are extremely rare. So much so, that I would automatically consider any 100% correct 1917 to be the product of some collector's "restoration" project unless there were other really compelling evidence to the contrary.
As Marty T implied, a rifle with a rebuild stamp will invariably have a mixture of manufacturers' parts. My 1917 has two rebuild stamps: RA-P (Raritan Arsenal) and 3GM-K. Last I knew, although the 3GM-K stamp is common, nobody as yet knows its source. Has any progress been made on this front?
"They've took the fun out of running the race. You never see a campfire anywhere. There's never any time for visiting." - Joe Redington Sr., 1997