the rule of thumb for chinese SKS is that if the serial number is 7 digits, the first digit is the amount of years since 1956, in your case 2, so your chinese SKS should be a 1958 production. obviously there is more to it but that is the basic gst of it that works on a large number of chinese SKS.
here is a thread that does into much greater detail with dating of chinese SKS and factory codes.