The first picture shows the chamber that holds the popcorn and this chamber lowers into the oil. Notice the electrodes sticking down from the bottom.
The second picture shows the copper straps in the oil chamber that contact the electrodes on the popcorn chamber thus completing the circuit.
I do not see where the heating element was attached. So my theory is it was attached between the electrodes.
This setup is very unsafe and I will modernize this setup, but I am just curious as to how it worked.
Any thoughts?
Pics here:
http://1937popmatic.blogspot.com