This wonderboy romset runs on a system1 1985 pcb with some flying wires.
Serial number of the pcb is 257

There are 2 piggyback boards:

The first is marked "SEGA 834-5764"  and it is placed on the socket of the sega sys1 protection chip and on a eprom socket.
there are IC2 and IC3 eproms (I can't read the codes because the stickers are damaged)
There is also a 40 pin socket in which they have put an unknow 42 NEC cpu (they have scratched the codes) with pin 21 and 22 cut!

The second piggyback is marked "SEGA 834-5755" and it contains proms and some logic.