Weird Japanse SEGA Megadrive motherboard

[wyvernshill]

Hi,

I recently bought a japanese megadrive online, its filthy but seems genuine.
However i believe it to be a va5 or va6 version.

But it seems to have been modified.
All motherboards i saw had jumpers 1 to 4,they were connected on the motherboard.
My motherboard just has a empty hole for jumpers 1 and 4, there isnt even a contact there.

If i want to mod it to USA can i still do so and how ?

What motherboard is this ?

http://m.imgur.com/xWpDJOR,zRQVIqR

[mvsfan]

You have a VA6.