As far as I have been able figure out studying the two offered keyboards, they have an identical base, with some coloured yellow squares (green for caps), and then finalised with different layers of black on top.
If you look carefully at the top left of the Q, W and E keys on the shifted qwertY, you will note a square that looks slightly different when the light hits at the exact right angle. I'm 99% sure that this is the square for the symbols on W, E and R on the qwertZ. that is hidden by the black paint.
(On the preproduction-unit the green dot for caps was quite small, And was e