yeah, looks like a home made panel ontop. Since its home made, I would bet they cut down the drawer on the 3 player wide panel.
Only pit fighter, rampart, guardians of the hood (3 player wide panels), relief pitcher(2 player wide panel), and some super rare protos had 25" monitors in that style of cab.
I doubt it was cyberball, eprom or skull and crossbones as the marquee difference. Plus sticking a 25" monitor into the that cab is very hard without the 25" frame (there is maybe 1/2" clearance on both sides). But if it was a 19", bank on klax.