I'm sure it's later than second year
All the super early SKS were Factory 26 Jianshe Arsenal and were made on Soviet tooling. Those rifles even have Cyrillic letters in the serial numbers.
I think the guy is using the serial number dating method, but I think that only applies to Factory 26 (even then I think it's been debunked).
best way is to look at the components ie stamped vs milled trigger, pinned vs threaded bbl, placement of sling swivel, design of rear sight leaf etc