> No idea, whats the game?!?
>
> Six...
>
> System16 - The Arcade Museum

Thank you for the answer.
Unfortunately I've bought the st-v with no cartridge, so I can't tell if it was supposed to be used by a game or some kind of application.
Anyhow the only relevant things I can tell are:
0) This daughter board is an original Sega board.
1) The main board dip shitches have the following configuration:
JP4 = 3-2
JP3 = 3-2
JP2 = 2-1
JP1 = 3-2
which is quite unusual according to the st-v service manual.
2) Once plugged in a cabinet, the board complain for a missing cartridge (I've no games at the moment to play with) and there is no extra test menu entry in service mode (i.e. st-v standard japanese bios, so it is meant to be used by some kind of game/application)

I'm sorry, but I'm not able at this time to tell where this board originally cames from. I'm investigating about it.

Thank you again for your help.