You have a very early chinese SKS. About a year before the addition of the /26\ State Arsenal stamp and several years before the addition of 3-character "Type 56" designation stamp (五六式).
You have what is commonly referred to as a "Ghost Rifle". When these recent import Chinese rifles first began to appear in the US en masse via Albania (post 2010), collectors and and mil-surp enthusiasts had a difficult time identifying their national origin. With no Arsneal stamp to identify it as Soviet(tiny star on left side of reciever) and no State Arsenal stamp from China ( /26\ ), these serial-number-only rifles presented a bit of a mystery. No one knew if they were chinese or soviet made.
Because of the mystery regarding national origins, some collectors began referring to them as "Ghost Rifles". Many still use the term, despite the fact that it has been proven that they are Chinese guns (partially made in USSR and China). Some find the term "Ghost" annoying and misleading and refer to this early serial number pattern on Chinese SKS's as "serial number only" rifles. Which is boring, IMO.
The "Ghost" rifle serial range runs from around 2000 -- 213,000. Around the 213k serial range, the /26\ State Factory Stamp appears. Through extensive research, the date of the first /26\ stamp has been pinpointed to early 1957 (likely April when Jianshe /26\ became officially state owned).
Accordingly, your early 5 digit Ghost Rifle was likely between April and June of 1956...on of the first 15,000 Chinese SKS carbines.
It's a beautiful rifle. Appears to be all matching. The stock is in amazing condition, and likely refinished post import. But there is a possibility that it is an 'as-issued' carbine. Have you checked the bottom of the piston tube and the piston shaft itself to see if they still have the electro-penciled serial numbers?
I have two all matching Ghost Rifles in my collection. 187k and 210k serial number range, much later than yours. And though both of my stocks match, they aren't in nearly as good of condition...and I have no intention to refinish them.
I have to disagree with the above claim that the any part of this carbine has been reblued. It does not appear to have been reblued. Which doesn't mean it hasn't been retouched, but the photos don't seem to demonstrate rebluing. I have 7 early Type 56's at least four of them retain 75%-99% of their original bluing.
Great rifle. Nice get. Congrats.