What is the diffrence betwen a commercial imported version and a true military verson?

Are all sks rifles listed on the c $ r list?

They were made in more than one country, and there are more than a few variations of the "military version" For instance there are type 1 ,2 and 3 Russian rifles. Early Chinese type 56 rifles are almost identical if not identical mechanically to Russian type 3s. You also have Albanian, and Romanian and Yugoslavian SkSs. North Korea, North Vietnam, and East Germany made them as well. The only "export" models were chinese made. They have a pressed and pinned in barrel instead of the usual threaded and screwed in barrel. Some even have a stamped receiver. I'm not sure if those ones are C&R, someone that knows more on that side of it will have to chime in.

most of the Chinese rifles are not C&R eligible, except for the recent Chinese-Albanians.  It has to do with the date stampings (or lack thereof) on the Chinese SKS guns.

In the case of Chi-Com SKSs if it's not  Factory 26 or M21 marked it was not a rifle made in a military factory.

Factory 26 refurbed rifles for the commercial market too but could not keep up with commercial demand.

All the odd-ball factory codes you see are from refurb centers or manufactures that were spun-up to satisfy the commercial market.

Some simply refurbed/scrubbed existing rifles and applied their markings on them after they were rebuilt. Some were newly built rifles.

All those odd-ball SKSs like shortened, "sniper", and the ones that take AK mags were never Chi-Com issue.

Other than factory 26, dating Chinese SKSs is not possible, as these factories didn't keep or cannot provide production data to satisfy BATF for C&R qualification.

Approximate era ('60s, '70s,  '80s) can be determine by certain features.  Early SKSs had a screwed in barrel, later models are pinned.  Trigger guards went from milled to stamped.

Differences in bolt handles, rear sight, etc will give an idea when it was made.

Look here for the most info in one site.

http://www.yooperj.com/SKS.htm