For one the sight looks counterfeit to me. There is beat marks on the sight that would indicate it has been at least moved if not replaced (forget the finish match). It could be the light or the way the photo was taken but it doesn't look real to me. I've not seen an Inland barrel on an S'G' that has that much "Inland" hieroglyphics on it and the wear on it doesn't match the wear on the rest of the carbine. The slide has no wear where the receiver does. I've been wrong about finishes before but it doesn't look right to me. The finish between the barrel and receiver isn't even close. Not a hard fast indicator but..... Sorry, it just doesn’t look right to me.
USGI, the bolt rear end looks really bad in the one photo that shows the rear sight.
PS yes it could have had the hammer from the gate doubtful but yes.