OP - since stock is replaced your SKS falls into the "shooter grade". There's nothing special about it, most of skss on market are force-matched refurbs. Even though it might be "light refurb" with only stock replaced - it's still "shooter grade" category where most ppl don't care about originality and niceties of the look but rather about functionality and rifle condition. "All matching" means almost nothing in this category. Because all imported refurbs were "all-matching", with some exceptions when mags were mixed.
P.S. Original factory serialization included EPing gas tube, piston, rear sight, extractor. Some types of refurbs (but not all) also had these parts EPed.
P.S. Original factory serialization included EPing gas tube, piston, rear sight, extractor. Some types of refurbs (but not all) also had these parts EPed.