Judging by your serial number range (GC 01X,XXX), the fact that it appears to have a normal sized front pivot pin, lacks the large sear block pin on the left side.. and has the somewhat lighter color gray anodizing (Pre-Ban Gray) vs the later black anodizing.. I'd say $1,700 minimum if it is truly in great condition. If it is unfired and has the original box then it's likely a $2,300-$2,500 rifle to the right buyer so long as it doesn't have a lot of handling marks. Does your rifle have a small sear block pin on the right side (smaller than the picture posted above), lack the restricted markings on the right side of the lower receiver magwell, and have a C M marked upper receiver with an engraved [C] and/or Triangle stamp mark in front of the ejection port door?