Your friend has a really really nice SKS, the pitting notwithstanding. The "dial" on the side is the base for a grenade launcher sight, and it does have the gas cutoff for launching grenades. Your friend needs to immediately attempt to locate the paperwork he got with the weapon and if the father is still alive he needs to get him to write a statement as to the capture. He should also see if the rest of the sight was captured with the rifle and if they still have it. To be all original it should have a blade bayonet, not that spiker I see in your photo. It would have most likely come from Vietnam. Value - should be $2k to $2200. If he can find the rest of the pieces I mentioned above, maybe a tad more, tho a spike bayo and overall condition will hurt some. If it really is his father's bringback - priceless.