Again, only for those who are interested:
I once had a student, after this presentation, challenge me on the uselessness of the 1947 hammer block, something like:
"Yes, but what if the rebound slide has hung up and fails to move forward, and then the gun is dropped with the hammer sitting on a loaded round?"
"And the operator doesn't notice that the hammer hasn't rebounded to its normal at rest position after the last intended shot?" I asked.
"Yes," said the student eagerly pressing his point.
"And the operator doesn't notice that the trigger hasn't moved to its forward rest position after the last intended shot?" I further asked.
"Yes, that too," rejoined the student, a little less confidently as he began the perceive the improbability of his hypothetical.
"Well, in that case, the hammer block [referring to the 1947 hammer block] isn't going to prevent the round from going off either, since the position of the hammer block is governed by the position of the rebound slide."
"Oh . . . yeah."
I actually gave him points, both for thinking enough to pose the question and in utter confidence that at the end he'd better understand the rebound slide/hammer block function than anyone else in the group.