Ok I'll chime in.
Regarding the barrel. Did you retract the op rod and look for markings under it, between the stock and rear hand gaurd? You should be able to see a manufacturers mark there.
If there is nothing there see if the owner will let you remove the rear hand gaurd, sometimes the marking is under it. In any case you should be able to see a manufacturer on the barrel.
As far as the price is concerned, what do you think he will take? If it's in reasonable shape $695 doesn't seem so bad. Unless of course you qualify for buying from the CMP in which case you should do that, price will be $500 plus shipping.