Brian writes… [via]
I found these electromechanical vane displays on eBay and accidentally won them. So, here they are! These are seven segment displays. Each segment is painted a bright yellow and fluoresces under UV light. The segments do not actually draw any power except when they are moved. Behind each segment is a solenoid that flips the segment on or off. Several units are then daisy chained together to form larger numbers. Watch the video below to see it in action and be sure to check out the image gallery.
Staver Electromechanical 7 Segment Vane Display - [Link]