The .22 mag could also be for a Colt Service Model Ace (SM serial prefix) which were ordered by the military beginning in about 1935. They are originally blue with a matching-numbered slide and many were parkerized when rebuilt. With either finish, these are expensive pistols and hard to find. If so, it's a scarce mag. Those I've had have had the diamond with "Ace" inside on the base and were blued.