A display device comprising a plurality of prize balls, a ball holder adapted to hold the balls in an individually controlled manner, a controller adapted to select a prize ball, a display mechanism adapted to display the selected prize ball to the player; and a positioning mechanism in communication with the controller adapted to position the selected prize ball relative to the display mechanism. The photochromic compounds according to the invention are characterized by two distinct absorption bands of the open form in the visible wavelength range, i. The riser of the first step has a very low height so that a gap between the plate member and a fragile semiconductor wafer bonded to a carrier having a peripheral abutment surface resting on the run of the first step, limits the bending of an edge portion of the wafer in a direction towards the plate member while the wafer is partially demounted from a wafer carrier.