Romanian, Yugo, Albanian, Russian, N Korean and N Vietnamese SKS are all C&R eligible as long as they are in their orginal cofiguration.
Chinese SKS are NOT C&R eligible - because China refuses to provide the ATF with a way to determine when the weapons were mfgr.
A C&R is a type of FFL... It is an 03FFL "Collector of Curios and Relics". It has the restrictions of the holder only being able to use it to aquire C&R approved firearms.
50yrs old (or older) and in it's orginal configuration is the qualification for ANY/EVERY firearm to be classified automatically as a C&R - unless it is specifically called out in the list (for example some commerative COLT pistols and the little 9X18mm CZ82 which are less than 50yr old).
Will