The barrel drawing number ending in 555 should be UNDER the rear handguard on top of the barrel. It appears your scope mount does have rounded ends on the hinge pin so I would say it is genuine USGI. Without paperwork to substantiate the rifle you will always be told it is worth the value of the parts. It could be a genuine USGI M1D but without definitive paperwork to prove it you have what must be assumed to be a parts rifle.