This was shown as darkroom timer with the lamp being a red flashlight bulb. A simple low frequency timing idea.
At the bottom left is pendulum lever connected to wall or shelf about 42 inches long, with the pivot point at the top having washers as spacers on pivot bolt to reduce friction and the resistor is a 3 to 5 pound weight that is adjustable up and down on pivot lever with set screws to adjust timing to one second light flashes.
The space at top of lever is where brass strip mounted stationary brushes second brass strip at top of pendulum lever to flash light ( square wave generator is only to run in simulator) when circuit is turned on and you start the pendulum swinging count the 1 second flashes to do timing,
