from Vista-
Does the 442/642 contain all the same internal lock mechanisms (e.g. - the flag) that the exposed hammer models have? Does the 442/642 contain all the trigger/sear etc. mechanisms necessary for single action shooting that the exposed hammer models have? Obviously, a couple of close-up internal pictures would be great...
Vista-
Welcome, though I am not official greeter.
Responding to your two questions:
1. Short answer: Yes, in reference to the ILS only.
Lock Arm (aka the "flag") says "Locked" even though it's internal. I just removed it and left everything else alone. This is probably not necessary but I did it for peace of mind, if nothing else. Removing the Lock Arm alone disables the entire ILS.
But there's no hammer block as in older J-frames (there's an internal firing pin with the newer ones).
The ILS is more of a storage device, in my view. It is certainly not a manual safety, but is engaged to avoid unauthorized use-like 'kids' or 'criminals'.
I'm not expert or a gunsmith but if you drop the gun without the ILS engaged there are other safety mechanisms to protect from a AD in spite of no hammer block.
The trigger must be pulled fully to the rear in order to fire. The ILS only prevents one from pulling the trigger in the first place.
Perhaps someone can give you a more detailed answer than I. I do know that the rebound slide locks the hammer and keeps it stationary unless trigger is pulled.
There's more to it, I believe. Help!
2. No, sort of. It's not relevant because there is no way you can shoot it single action, even with the sideplate off, AFAIK. So forget 'poor boy's trigger job' or cocking the weapon.
With your Centennial, you can 'stage the trigger' once you've smoothed it out. Some people do not think that's a good practice.
For future reference with respect to exposed hammer DA and SA revolvers - "poor boys trigger job":
http://www.gunblast.com/Poorboy.htm. (I've only done the first step of the procedure, and have found it quite helpful even with semi-autos that have exposed hammers and can fire SA, or DA/SA. Follow his caution about not overdoing it. It could result in push-off, though he does not specifically state that).
Anyway, I am not a gunsmith. Best to you!