ok mine is is an MS111 which looks older than the one you have it is wired as follows.
according to the markings on the board (screw terminals on mine)
+12 (hooked up to original cabinets psu)
Gnd connected to original Cab gnd and to Jpac Gnd
Cred goes into Jamma harness but if used on an Ipac would connect to Coin1 input
Lamp Not connected
Mtr connects to my mechanical meter (not required)
My mars system has a cable between the actual coin slot and the board, you may need to make yourself one up as it does not look as if yours is connected in your picture.

