The clock is battery driven, but indirectly (by modern standards), the chiming mechanism winds a main-spring in addition to moving the chime striker. The main-spring operates what appears to be a pretty standard pendulum clock mechanism.That explains how the movement is powered and it explains why the clock abruptly started working yesterday. Recall from the last post, I said, "The chime mechanism works, because somehow while fiddling with the thing yesterday I triggered it; the motor ran and everything worked correctly."
When the motor ran, it wound the clock; but because it's not chiming on the hour and half hour the mainspring unwound, and that's why the clock stopped.
So: just have to fix the chime mechanism, and then we'll be good to go!
So, took it all apart again, and had a gander. The main problem is that the motor for striking the chime connects to the negative terminal (ground) through the movement frame, and although the ground lug was in contact with the frame it was not good contact. Moved a washer from one place where it was totally f-ing useless (I think someone besides me had this thing apart) and put it there, and now it makes a good connection and it will chime when the time is right. And it's happily ticking away again.
It really helps to know how something works, you know? But we'll see if it's actually fixed for good and all, or if there's something else I'm overlooking.
Only--pun intended--time will tell.