Early Wii Console prototypes

 
Black Wii
The disc slot seems to be longer, and slim as shown in the next picture. I can't tell if the where the buttons are, but I'm pretty sure they're the same as shown in the next picture.

White Wii
The nun-chuck's adapter looks like the Wii Motion+ accessory. The disc slot appears to be more slim, could possibly damage the disc, The RESET and EJECT buttons are together, rather than the final version of the Wii having it's RESET button up top.

Back side of the Wii. It appears that the power adapter, (or maybe I'm wrong and it's the sensor bar cord) is black.