Look at the front sight - if it slips over the muzzle, like that of an '03 - it's a cut-down piece.
Originals were silver-soldered and the join blends with the barrel's contour.
The rear sight should have a 'C' on the sight base, as well.
Is there more?
Certainly - but this is fast enough for now.
Good Luck!
Scouts Out!