is there anything on the underside?
i'm guessing the board plugs into the rom socket on the motherboard underneath, since there aren't enough wires connected on the black connector to provide the data and address lines needed to address the 4k rom
i'd guess the connector is just there to pull the address lines and data lines needed to do the bank switching. it might be possible to make a guess at the address used to trigger the bank switching if we knew which pins were connected to which wires and what the pinout is of the socket that it connects to.
Darren