from memory it was the number. I will have to dig up old photo for the exact number but my understanding is that's the number to indicating Sega Japan's internal asset or something belong to their division?
I am so jealous of the lucky SOB who got his hand of this! I feel giddy enough to have mine with such a low serial number, B40000411, so I guess the 411th retail unit ever made! Sadly, I can't see the two images you had posted.
it was not the retail machine. the MB rev was one before the launch machine plus few Dev stuff carried over. dumped all the photos I took over here - dj898.egloos.com/3006624