Markings.
$100 to over $1000, depending on the specifics.
they are about $100
Around $300- depending on condition and originality
Is it marked with Chinese characters or in the Cyrilic alphabet? <><><> As above. In addition, MOST Russian SKS rifles had blade style bayonets. MOST Chinese rifle had a spike type bayonet. But marlings are the defintive answer.
This is purely opinion on my part, but the SKS was created in Russia, and made there for a number of years before the Chinese began manufacture. The Russian SKS tends to have better quality machining than the Chinese. Both are good, but the Russian is the original, and the better built rifle. Examine one of each side-by-side, and see what you think.
Dependent on condition, anywhere from $300 - $500.
It's the marking of the arsenal which manufactured it. In this case, it would be the Tula Arsenal.
Priceless, since a true SKS assault rifle would be a prototype only most likely. The SKS fires semi-automatically and does not have provision for full auto fire. If you have a normal run of the mill Chinese SKS it is worth 100-400 or so depenidng on condition, box, accessories, etc..
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Russian
Very similar, minor differences,