I recently obtained a nickel finish single action army model "Colt" It has matching serial numbers - 169550 and is barrel stamped "COLT'S PT FA. MFG. CO. HARTFORD CT. USA." according to the reference material I checked, this stamping idicates a rather rare London model. The problem is the revolver has a spring loaded cylinder axis pin button which is not consistant with that serial number. Is my standard catalog wrong or do I have a well made copy? (Even the face of the cylinder is stamped with the Colt logo.) If it's real, what is it really worth?