GB Dev cart? What is this?

I've bought this in Superpotato, Den Den Town. Price was on the low side and I saw the prototype look of the cart. It has an official Nintendo EPROM pcb.
When turned on, it shows the screen on the first pic. You can move the text around and reset the position with Start + Select.
But what is this? Was this used in some dev kit?
Thanks

Nicola

 

You have no clue?

 

No idea, though it looks pretty cool.

Are you interested in dumping it/ having it dumped?

 

I've just bought an EPROM programmer (cheap willem) so I'll see if I can dump it. I may try also with a GBXchanger. Wait, I'll try now

 

Ok, dumped with a GBXchanger, but gives a checksum error. It's 32KB
and, in Hex Editor I can find this ASCII: "DMG-CAD (IBM-PC) SUPPORT PROGRAM VER. 1.02 BK."

Later, a serie of characters (@ABCDEFGHIJ...) and "DMG-MMM01"

Nothing more. It runs on emulator.

the EPROM is a Toshiba TC571000AD-150 Japan 9339EAK VPP 12.5V

 

Maybe it would be useful to understand the DMG-CAD.
DMG is Dot Matrix Game (the Game Boy) but CAD? Computer Assisted Device? Control And Debug? Ctrl Alt Del?