Our good friends at the big house of N have relayed an official comment about the contrast control that was discovered earlier this week. It's not a contrast control at all. It's a flicker control! Here's the official Nintendo statement about this...

"A positive and negative voltage controls Liquid Crystal Displays (LCDs). The "contrast control" that you are referring to is actually a flicker control. The adjustment is used to synchronize the positive and negative voltages. If these voltages are out of adjustment then the LCD will no longer respond correctly. The result will be an excess charge built up in the liquid crystal and permanently damage the LCD. The excessive charge gives the appearance of a brighter screen because the liquid crystal is not reacting properly to the voltages applied. When the adjustment of the voltages is correct the changing polarities will not allow a charge to build up, which prolongs the LCD life.

This adjustment is set by the manufacturer or must be performed by a qualified Nintendo Technician using proper equipment (Proper lighting, special tools, test equipment and software). Adjusting the flicker without the proper tools and lighting will put the voltages out of sync and may cause damage to the unit."