Truly "all matching" rifles are hard to find. Generally to be all matching they need to be found as un-issued. Even the butt-plate should have an electro-pencil serial number and the gas system. This electro-penciling is original. There are many matching rifles, but the butt plates have been refinished (light re-furb) or the stamped parts are all matching but the metal has been refinished so the electro-penciling on the gas system is missing. All the parts on the above two variations are probably original to the rifle, just they went through a refurb (light to moderate) so they are missing some truly "all matching" serial numbered parts. Sometimes the butt plates were re-finished simply due to some minimal wear on the butt plate in an arsenal rack, so the minimal refurb may just be some dabs of paint on the butt plate.
The other place people don't check is the bolt/breech block, when you take it apart, many rifles have mm firing pins etc, but because the cocking handle is matched to the rest of the rifle many people never check the smaller components to see if they are matching.
More heavy refurbs usually have the tell tale signs of the refurb stamp on the stock or top cover.
The other links will help too.