Was following a thread over on subguns.com on the match of Colt upper and lower finish. Some of the experts over there stated the finish must absolutely match or the gun is not factory. Since photopoint was down I whip up a new album of factory Colts, showing finish match of the receivers. The experts on subguns have not responded to my post, but as fellow students of the Colt AR, I’d tough you might like to see the photos.
Nice Pics. I have a transitional r6601 just like your 6551 and they matched up about the same. However the new M4 upper I put on it that I purchased when they first came out is a dead match. Go figure.