I recently acquired an as-found cast iron inner box that I'll be cleaning up and restoring, a couple of wires are broken and at least one other has been altered/cut/partially replaced, and had a modern plastic wire nut on it.
It's pretty dirty and someone put loads of oil in the mechanism, so much so that when I wound the spring up oil oozed up to the surface...

This is the first master box I've owned which has the "set/not set" indicator and reset, so the exact function of it's additional trip mechanism is not familiar to me. I can see how it works- a pulse to the coil trips the mechanical linkage and starts the box remotely, but my question is, where and when does the current pulse come from that activates the tripper coil?

Am I correct in assuming a building's local FA system would be the source?

The tripper coil's wires are broken, here's a photo: