Edge illuminated numeric displays (link shows a modern
version... the
old ones used grain of wheat lamps):
http://blog.makezine.com/2012/02/18/edge-lit-led-nixie-tube-display/
Ah yes, I have a DVM somewhere that uses those...
O also have a Trend datacomms tester (essentially a bit error data
tester) with the largest number of different display devices on one panel
that I've ever seen. From memory, there is :
A mechancial slow motion drive/scale for the variable capacitor (!) to
set the baud rate (you might not call that a display device though)
Assrorted coloured filamant lamps for varions status signals
A row of white filamanet lamps displaying a 10 bit error counter (in binary).
The overflow of this counter is counted by an electromechanicla digital
couter (I forget if 'overflow' is every 1000 counts or every 1024
counts).
A pair of those edge-lit displayu for soemthing-or-other
A centre-zero moving coil (analogue) meter to display signal bias.
-tony