I just brought this home and the only gripe about it is that it has a stupid internal lock. Do all Mark III models have an internal lock? My buddies 22/45 does not have one.

Yes, the Mk III models have this internal lock, a magazine disconnect, and a Loaded Chamber Indicator (LCI). These are things their lawyers demanded so that they could sell in Commifornia, and other socialist states.
Brian
At least Ruger hides the lock, many others do not. I'm afraid the lock on guns will only become more common as time goes on, rather than making different guns for different states.