A mechanical seven- or sixteen-segment display is feasible. Here's an electromechanical type which was used nationally as railway clocks for a while: http://www.youtube.com/watch?v=djcaR1tVdVg While this example (designed for numbers only) is merely seven-segmented, a sixteen-segment version could display letters quite competently.
The obvious way to drive one without electricity is with pneumatics. You would need to build some fluidic logic to store a six-bit character code, and then decode it to drive the individual segments. It doesn't matter if the decoder is a bit slow, since you only need to latch the code into the storage before you can move on to the next display position.
Input on the bottom row could be done by mechanically actuating the storage valves with a sliding camshaft. Slide the cams under the position to be updated, then rotate the appropriate ones to "set" or "reset" the bits required. A separate "group reset" lever could be arranged to zero the storage registers in the entire row.
Additional rows above could be driven from the bottom row, and filled by scrolling. A tradeoff could be made here by sending the decoded signal up for latching directly, rather than duplicating the decoders.
Biting the hand that feeds IT
