Interesting! I reckon this card is actual arcade hardware rather than a development tool. I can't find any references to Data East PC-based hardware so this is either a prototype or something rather esoteric.
The card acts a flash disk (the LFDC-1016 is a flash disk controller IC) and thus the Microsoft sticker is the MS-DOS license. It appears there's 2MB of flash dedicated to storage; I'm assuming that the actual game/software would be stored on a CD and that the flash disk is only used to boot the system. What are the contents of the disk? (perhaps you could take a photo of the root listing?)
It appears a further 2MB of flash is dedicated to YMZ280B sound samples. A dump of the flash may yield some clues.
Presumably the backplate connector would lead to a JAMMA or I/O interface board.
Could you provide photos of the other hardware components? (motherboard and video card in particular)