This post should be moved by an Admin to the Colt Semiauto Pistols forum.
It appears that the original serial number was removed and the "C49" stamp was added. The "KK" stampings may be inspector's marks. Can you show full side-view photos of both sides of the pistol so we can see all of the markings? Based on the last patent date, the sldie was manufactured between s/n 20000 (1909) and 300000 (1921).