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.
Very similar, minor differences,
Markings.
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.
Value of ANY gun is based on exact make, model, and condition. A well worn Yugo SKS may be $150, while a pristine Russian SKS is $500. An average Chinese SKS is around $250-$275.
No. ALL SKS rifles - Soviet, Chinese, Albanian, Yugoslav, Chinese, Romanian, N. Korean, N. Vietnamese and East German - are chambered for the 7.62x39 M1943 cartridge, and can facilitate only that cartridge.
=== === === ===
Russian
they are about $100
Importer name
Depends on country of manufacture and condition. I am not aware of any publicly available serial number lists for any of the SKS manufacturers, so that is not a helpful bit of info. Russian SKS carbines are the most valuable at this point, with some in excellent condition reaching $400. They are followed by Chinese and Yugoslavian. A beatup Yugo with a rusted gas valve will fetch $100 on a good day.
They began production of the Type 56 carbine (the Chinese designation for the SKS) in 1956, and production (for the civil market) continues to the present day.
20-45 USD