BTW, it is generally believed (and I have stated) that a center fire revolver will not USUALLY be damaged by dry firing. But I think a broken firing pin of that type can be caused by dry firing. The firing pin won't necessarily break during dry firing, but it is stressed and a crack started which can show up later.
I don't consider this a major issue (and I still fire my revolvers occasionally without snap caps), but it is a consideration. I have little doubt that S&W's change to a frame-mounted firing pin was made at least in part to prevent hammer nose breakage. It is the kind of thing that happens rarely, not enough to effect a change in manufacturing, but is "on the radar" to be addressed by the manufacturer when/if there is a major redesign into which the change can easily be incorporated.
Jim