When I was 7 or 8 years old, my father made nothing boxes. He explained in simple terms how a neon bulb turned on at a high voltage and remained on until the voltage dropped much lower. By using this feature he could make the bulbs flash. Flashing forward about 30 years my uncle gave me a nothing box my father made. It was the only one remaining that I know of. I dissected it carefully and got it’s very odd circuit that is shown below. I do not know if he designed this, found this in a magazine or derived it from the typical circuit you find online today. It is the only one I found with the capacitors tied together and take to ground through a separate resistor. Bulb GL9 is special. When the voltage finally build up enough for it to fire, it turns off all of the other lamps until it drops the overall voltage enough to turn off which them allows the others to begin flashing again. As best as I can tell, there is only ever one bulb turned on at a time.
Here are pictures of the original Nothing Box and my mine. They are basically the same circuit except the layout and the original one worked off of a 90 Volt “B” cell and mine has a Maxim 1771 chip to generate it’s 90 volts from a 12VDC wall wart.
Take note of the Switch inside that my dad used to switch the operational mode. With it up, the center bulb did nothing, with it down, when it finally fired, the others turned off until it went out. You can tell he worked on industrial sized batteries by the industrial size of that switch!
Enjoy this short video showing both versions running