Looks like a re-blue to me. Over polished in some areas and under polished in others -bluing over pitting.
Barrel was marked COLT D.A. 45I agree that it's a reblue - I know these came in .45 Colt, but I'm not sure how the barrel was marked. Also this guy has quite a few other Colts for sale! A good amount of SAAs and 1911 variations.