Cart Reader V2
This is an older version of the Cart Reader that only has SNES and N64 slots.
This Cart Reader features an additional USB port on the back that can be used to achieve a 3.3V supply without the need of modifying the Arduino Mega itself. This means that every time you want 3.3V you have to use this second USB port at the back of the shield and lose the ability to use the Arduino Serial Monitor. This was fixed with later versions which only have the one USB port on the Arduino itself.
This hardware variant runs the same Cart_Reader Arduino sketch as the others and can be updated to the newest version without any changes.