I have three old replica colts from the late 60s... best guess after researching is ASM but they are completely defarbed and “antiqued.” I have been trying to figure out a timing problem with the 3rd Dragoon but I couldn’t get the right rear back strap screw to budge. Broke a couple of my good gunsmithing screwdrivers. The slot is very thin so the tool has to take a lot of stress. Anyway I soaked it in PB Blaster for a few days and broke another screwdriver. I cycled it with a propane torch and kept reapplying oil and checking every couple days. Tonight it finally came free. So then of course I promptly lost the left rear screw somehow. I don’t understand this. I only had one screw out. I had it on a magnetic pickup tool so it wouldn’t get lost. I finally got the frozen (right) screw out. I picked up the screw off the magnet thing. And now I can’t find one of the screws. The one that was on the magnet. It’s like it vanished. I’m completely flummoxed. Check out the verdigris and decades years worth of dust and oil. It’s only been shot once to my knowledge and that was 30 years ago.