> there's a fourth one which has an extra key on both the right and the left side of the keyboard. An example is the Brazilian Portuguese layout Model M (pic: .

> there's a fourth one which has an extra key on both the right and the left side of the keyboard. An example is the Brazilian Portuguese layout Model M (pic: ...) That's the ABNT2 keyboard layout, which is the keyboard layout used here in Brazil. AFAIK, it's the only common keyboard layout with that characteristic.