What exactly is this? There is a scope mount on the side, so it's not military. What is it worth, if all the number match and it's in good+ shape?

It's called a Cowboy Companion marketed by Navy Arms. Worth maybe $300+ or so would be my guess.

Is the barrel length right for the Cowboy Companion? What are the giveaways?

Ahh...off the top of my head maybe 350?

I think so 18"? The scope mount is the giveaway.

The last CC scope/mount I saw sold for $260.00.

A CC without the base was called the "paratrooper".

Of course both are fantasy SKSs and were never PLA issue. Just a shortened SKS made for the export market.

The last CC without scope/mount I saw sold for around $600.00.

When you consider it $600 is the deal of the day if you had to pay a gun smith to shorten a SKS and install a scope base for you.

BTW....Barrels on the CC and paratrooper are 16".

My "paratrooper".

No.  It's not a "Cowboy Companion".  Those had the shorter 16.5" barrel like the "Para", and no bayonet.

This SKS has a standard length 20" barrel and a bayonet.  Navy Arms offered standard Type 56 SKSs with a side scope mount added.  

See "A" in the below ad.  The Cowboy Companion is "D".



(Click on the photo to enlarge.  Even larger version here: http://i177.photobucket.com/albums/w201/SVT-40/Misc%20Stuff/OneTouchFeb2320071-1.jpg )

Navy Arms also had a few other standard 20" barrel SKSs with side scope mounts, but those included bipods mounted on the barrel too.  Like the "Sharpshooter" ("C" in the above ad) and the "Farmer's Friend" (not shown in the above ad).