Woah, I wish it were mine!!!! That was just some rando pick offa the www.
I agree.
I was really surprised that the 642s wouldn't have a hammer block. Then I remembered that the "Centennial" (that were referred to as "Lemon Squeezers) had a grip safety, wonder if the grip safety interfered with the hammer safety?
ETA: That should be an early 42, the predecessor of the current 642 (6 being a stainless gun).