Saw an old M1911 in a gun shop in Memphis with an early US Army slide with a stamped serial # of MM5127 on the right side. No markings of any kind on the frame. Most probably a cobbled together gun, but I have never seen that type of serial #. The gun had the same finish all over, not blued, but parkerized? The slide was the old type Colt with the circle Colt behind the serrations. Any ideas?