Deeton451, Thank you for your reply. The information helps a lot. The bit about sending the parts out for blueing was enlightening....I hadn't thought of the matching issue! I think with what you've said my question is answered. My barrel doesn't appear to be numbered, only marked on top with "Colt .45 Auto". As a Detonics historical novice I believe its original as the rest of the gun appears to be. I just wonder if there is some knowledge out there of these particular markings.

Thank You,
MK1