It's from a Killer Instinct 2 machine (dedicated cab) and it's connected between the coin mechanism and the game board, and also to somewhere at the top of the cab where I can't see (and don't want to venture) and probably to the power supply or something. the game board is no longer in use - i've put an ssf2 cps2 combo in there instead and wired it up.
I'm trying to change the machine from freeplay to coins, which is straightforward, but the coin mech will only take £1 before sending a pulse and i want to change it to 20p (I'm in UK).

Seeing as it doesn't appear to be configurable, it's got me wondering if the KI2 game board itself handles the money. I'm gonna go try my xbox KI emu in a sec to see (I'm assuming KI2 will have the same sort of setup), once I figure out how to go to the options...