"Lamp limiter constructed! " Well done.
Din plugs/sockets sometimes have tiny numbers on the back, but there's a chart here -
https://www.electronics2000.co.uk/pin-out/dincon.php and here -
https://en.wikipedia.org/wiki/DIN_connector You should be able to figure out what's what when you take the top/bottom off and follow the wires from the OPT (output transformer)
Good to see you making progress, Andy.