Concept: display is a large board of metallic pins (like the 3D pin art). this display shows the time projected mechnically at certain time intervals depends on user need. The digits are embossed by the 2 Axis moving head on the back. This head is controlled by an Arduino or a microcontroller.
First it receives on-signal that energizes the coil in the head tip making it magnetic so that it can pull back the recently embossed time and therefore flatten the display (i.e: wipes out the board).
Then the head received an off-signal, so it is no longer magnetized, it then pushes the pins to the outside to draw (or plot) the new time.