There are two types of Colt revolvers and they are not equal. The Python, Official Police and Diamondback all have the 19th Century lockwork. So did the Agent, earlier Detective Specials and Troopers. The MK III Trooper introduced a S&W type lockwork. Later Detective Specials and the King Cobra and Anaconda used the newer Trooper type lockwork. You can distinguish the action by looking at the location of the side plate retaining screw. The older guns have the screw near the bolt hole (cylinder stop) and the newer guns have them closer to the front of the cylinder.
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