that one is rare.
kevtris: boxing Identification.png grid 3/5 there's an unlabeled plate in the middle
*edit* I added it to MESS. I'm guessing it is plate #8.
According to your pinout description, pin 13 is speaker-out, but in MESS I only get sound out of pin 11.
I also added VTech Invaders, but it's not playable. Hopefully that makes it easier to find out what causes the remaining MCU emu problems (for this game, and Coleco Galaxian).