Now back in the day, you could twist the old school metal knob and then a little flag printed with the words "" or "Epoch Fail" would pop up. It looked a little like this.
Presumably, the Parking Control Officer (not "meter maid", Heavens no!) would investigate and then call the service people. Parkers wouldn't have to pay (but would risk getting a ticket if they stayed over the time limit for parking in that area).
These days there's no knob, so the PCO can't easily tell if the meter is operational. But you can see for yourself the tell-tale coin indicating a jam. Larger version of this photo here.
Anywho, we notified the meter fix-it department (415 290-4090) and we drafted a letter to the Citation Review Center. Wish us luck.Violation