I'm researching my MK1 and can't seem to find the information I've run into in the past. The frame is marked "I 4XXX" and the slide is electric penciled to the same. The barrel is not marked from what I can tell except for a stamp on top that says "COLT 45 AUTO"(yes, I've stripped it and had the bare barrel in my hands). Is the barrel correct? I thought I had read in the past that the barrels were also serial numbered to the frame/slide.