Okay so no super gun. This is a MVS1FS board which has x2 controller ports built in.
Power is from a 5V 3 Amp PSU (it’s a PWR+ model which has been fitted to power the board via the 5v jamma connection)
I’m pretty sure it is CSYNC the voltage was the usual 4-5 volts and had to be lowered via the resistor. Also the cable from retrogaming cables is wired for a Neo geo CD CSync.