A magnetically operated display unit includes a frame of a color, a plate pivotably mounted on the frame which includes a first surface of a color different from that of the frame and a second surface of a color identical to that of the frame, a magnet embedded in the plate, a U-shaped ferromagnetic...http://www.google.com/patents/US6025825?utm_source=gb-gplus-sharePatent US6025825 - Magnetically operated display
