Eagle makes great lowers. Their pre-ban lowers rank right up there with the best.
You will not find pre-ban Eagle lowers going for less than $600.00, and thats considered a steal...let alone a complete pre-ban rifle.
Your receiver should be marked:
Eagle Arms
Coal Valley, IL
According to the Armalite website...if the serial number is less than 30000, the lower was manufactured prior to the ban, but you will still need authentication from the owner that he assembled it into a complete rifle before the ban took effect. If it was sold as a complete rifle, Armalite can furnish you with a letter of authenticity.
I would jump on it regardless of what the "finish" looks like (if its a pre-ban).
DPMS can re-anodize and coat with black teflon for $55.00. I had this done to one of my eagles and it came back looking new.
You have to be careful of refinishing offered by others because they have to sandblast the surface in order to apply their "new and improved" finish. Just ask them...An example would be gunkote, bearcoat, etc... What this means is that the anodizing is removed and the new finish is applied over the degreased bare metal. Remember anodizing is what gives strength to the aluminum receiver. These new finishes may be "hard" and "durable", but its not as hard as anodizing.
Yes, DPMS has to sandblast the old anodizing off (but at least they are putting it back on). I did not loose any tolerances on my lower. It fit just as tight, if not a little tighter when I got it back. Plus, I had the peace of mind knowing it was still anodized to spec and looking new.