You can't trust the date shown on the NMK games, we've seen multiple cases of completely different builds with the same date, and even different games with the same date. Either they forgot to update it, or it has some other meaning like the engine date, or project start date, rather than the build date.
Likewise NMK don't seem to do anything to differentiate versions with labels.
The only real way to know is the dump them.
If Yotsuya is willing to dump some ROMs from his PCB, which ROMs are most likely to show if there is a different variant?
- a03 looks promising. (main CPU)
- a08, a09, and a10 might have something relevant. (proms)
- a01, a02, a04, a05, a06 and a07 don't look very promising for the difference noted. (audio CPU, oki sound chips, tiles, and sprites)
921a03 0524288 maincpu
921a02 0065536 audiocpu
921a01 0131072 fgtile
921a04 2097152 bgtile
921a07 2097152 sprites
921a05 0524288 oki1
921a06 0524288 oki2
921a08 0000256 proms
921a09 0000256 proms
921a10 0000032 proms
Scott