Hi,
according to the schematics on the pic (and the game-board-schematics) is pin 7 the ground connection to the
coin-button-switches, slam-door switch and start-button-switches...
if it is the original wiring:
the one orange-red cable (that is still connected) should lead to the slam-door switch (on the inner coin door) and the loose one should lead to the start-button-switches and coin switch(es).
if it is so, it is the GND-Connection to those switches and should be connected to PIN 7
Greetings
Jochen