Thanks a bunch for the profile pic Opt2not. Looks like I have 4 contenders now. Especially in light of the original monitor not being in the cab anymore. I will check the dates of the other games, to see if any of those also fit the time frame.
Even though it could have been any one of those four cabinets,
Splat! is the most likely, since it already has the same control layout as Smash TV.
Next in likelihood would be
Bubbles and
Mystic Marathon. Both of those machines would have required altering or replacing the control panel/controls; in addition to the new board, artwork, and JAMMA wiring.
Sinistar is the least likely, due to its vertical monitor (though if it is easily rotatable like in a Dynamo cabinet, then it wouldn't have been much of a hardship to do so).
Look at the underside of your control panel. Has it been modified? Look for extra holes that have been patched/filled. If you don't see any, then it is almost definitely a
Splat! cabinet (or at the very least, a
Splat! control panel).