The 7800 devOS is universal. It will work as either PAL or NTSC depending on what type 7800 you install it in.
You should be able to dump it without a display though. After you plug in the cart and turn it on, hit the reset button on the 7800 and it will go into transfer mode.
Mitch
Never seen a 2600 proto quite like that. Hope you can dump it (and hopefully release it) soon!
Can you tell if it is a WIP or is it the final version?