The electro-penciled numbers are generally "assembly numbers", and do not correspond to the serial number. Check out the SKS forum at Tuco's Gunboards. Those guys have really researched this, and can tell you which serial number prefixes (the letter it starts with) should have which features (night sights, holes in grenade launcher, etc).
The price is alright, especially if they are in excellent condition. Last year I paid $159 for mine, used but very good. The unissued rifles command more, and the worn ones are as little as $115.
I was surprised how well mine shot. You should really enjoy them.
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