Id hand you $650 for it without knowing anything, just looking at it. Seriously.. How bad could it be... and IF something is not right about it, it's not expensive to remedy. If we are using polymer as major parts on these rifles, anything metal should be a step above.
What part is forged?
Upper, lower, barrel or just the paperwork....
While pencil barrels don't do it for me, that doesn't look bad and seems like a smoking deal.
There are some smoking Black Friday deals going around right now though....
I saw complete uppers at JSE Surplus for 335.00 with 1/7 twist barrels.
Like wakal said, do you want a wall hanger trophy gun or a shooter?
There are lots of very expensive guns in safes everywhere that have hardly been shot but the owner can brag about it...LOL!!
And there are lots of cheaper guns out there that have actually been used and taken game!
For $650 it's not terrible, it looks like a pretty good deal. Forged upper/lower, most likely carbine gas and an M4 profile barrel with the useless M203 cut.
Most importantly what's it's intended use?
If it's a range toy, then it should serve your needs. I'm not a huge fan of 1/9 twist but it will shoot 55gr no problem. If you're betting your life on it I have some better recommendations.
I would definitely recommend the 12 inch rail. It will give you a longer sight radius. Also in my short experience shooting carbines a longer rail generally gives you a greater range of possibilities as you grow into shooting it.