PT1911 Hammer lock
I picked one of these up on a trade a long time ago and the keys had been lost so I decided to remove it. I've read where lots of folks replace the hammer (and sear) but this isn't necessary.
Break the gun down to the point where you can remove the hammer & strut. Drift out the pin thats located above the hammer strut pin. With the pin removed, the lock will come out by applying a little centrifugal force. I popped mine a few times against the kitchen table and the lock popped out. Reassembled the gun and all is good. I'd read that these locks like to suddenly engage (like you hear about on S&W revolvers) so even if I had the keys I'd have done it anyway. Takes about 15-20 minutes to do.
Also, from my own experience, replacing the hammer without replacing the sear is an iffy proposition. I always use a matched set as this way I'm sure that the angles and tolerances are correct...