This revision is fairly well known, and is also a fairly well known construction technique. Each epoxy blob contains a chip die bonded directly to the PCB. A popular cost-cutting measure, which also had the nice advantage of keeping nosy hackers out of the hardware. Other than the superficial differences and of course the fact that you can't get access to the leads of each chip, it's pretty much identical to any other DMG.

EDIT: In other words, not a prototype, just Nintendo being cheap yet again.

I found this when cleaning a lot of  ebay gameboys, maybe from a "play it loud" ( i forget)  : 

DMG mother board -08 (right)    More or less has the same layout  as other versions,  but with mush smaller,  resin covered chips.  Has some different traces too and "spermy" looking solder pads in the center.      Obviously  this is a later version but possibly a protoype for pocket hardware?

Anyone know anything?