Help me identify this Sega Mega Drive motherboard revision....

So I just bought a Japanese Sega Mega Drive model 1 off eBay. To my surprise when I opened it up to clean it, I noticed the motherboard didn't have a revision number on it. It also had a little daughter board connected to the mainboard, with the Sega logo on it. I think this may be one of the original launch Mega Drives from 1988, can anyone identify it?

Pics:

 

http://segaretro.org/Mega_Drive_PCB_revisions

VA0 revision.

"Due to a last-minute issue with the VDP in H40 mode, additional clock circuitry had to be added during manufacturing. This circuitry is present on a daughterboard in the center of the PCB, and contains the master oscillator (53.6931 MHz, NTSC), a 74LS74 (dual D-type flip-flops), and two 74LS161s (4-bit counter)."

 

Ah so it was the very first revision, thanks. Any idea if this is rare? I was planning on installing region and language switches but if it is an uncommon console I may leave it untouched.

 

No idea if it is rare or not, sorry.

 

I doubt its rare, just most of them dont get opened and they are in Japan.

Same as the VA0 saturn - theres plenty of them.

 

They're not rare. I own a Mega Drive like that too. In fact I've had a few over the years.