A little sheet metal box somehow made it back home.
Between the gauges for the power plant boilers and the steam pump flywheels.
The newer tunnels were fitted with these fluorescent lights, although some skylights (block glass embedded in skywalks) let in some natural light during the day.
One of the older buildings on the site, this is an old power house that provided electricity to the plant. I spent some time walking around it and believe it was fired with coal gas but had a diesel backup installed later.
If there were no other options, operators could climb this ladder from the Communications Room to the surface, after opening two heavy steel hatches, of course.
I found a historical photo of this room showing 10-foot high machines with wires hanging by the mile from looms and schematic charts.
One of a few dozen steel bed frames left in the rubble of the collapsing building.
The steel sea leg is so heavy it requires a huge counterweight that travels the height of the elevator.