Re: Just use a CRT its not an anachronism
But DC Electricity dates from some time after 1798, at least in 1878 they celebrated a Volta centenary in France. (Not sure if his Birth, death or the Battery). I'm too lazy to look it up.
Actually there is even the alleged Bagdad Battery,
Two modern Steam Punk displays with memory ...
Actually modern DLP projectors use an array of hinged mirrors, doing 40 x 20 characters each made of 11 segments (starburst display normally uses 14, but 11 is possible) with mirrors or the eInk concept ( using rotating 1/2 white & black segment shape beads instead of balls of Kindle etc).
So we need to operate 40 x 20 x 11 = 8800 segments (either elongated beads 1/2 white & black or hinged mirrors). The beads need no additional light source, only need two positions, could have four faces, and are very stable.
The first electrical matrix displays may be 1908. Victoria died 3 years earlier?
12 segments need 3 columns x 4 rows . making the 40 x 20 text panel 120 x 80 X / Y multiplexed.
One set of 60 Punched metal cards can do the character encoding for each 3 x 4 character cell. The minimum is to reuse 1 & 0 for I and O (as old typewriters did) and only have one case = 26 + 8 = 34 cards / characters.
We maybe can share 5 and S and also 8 and B reducing it to 32.
Update of entire display is slow, maybe up to 5 minutes if a 1/2 second per cell is possible. Erase would be fast (1/10th sec) as that can be a single operation without character cell. Per cell access perhaps 1/2 second.
Each bead about 1/32" diameter and 1/4" long I think?
I actually have 4 x 3 matrixed 11 segment + dp (= 12) LED panels. Curiously most starbursts are 14, but it looks like a 14 segment. (some segments are tied together).
BTW LED was discovered about 1912 by a Marconi Employee but ignored. They were looking for a better RF detection crystal and a weak glow was of no interest. It was discovered again in 1930s by a Russian killed during WWII.
Victorian CRT (on Continent the Braun Tube) was VERY dim as it was "cold cathode", no heater/filament. It wasn't till after thermionic emission was understood (Fleming and De Forest, in contrast Edison was technically clueless, he was a commercial person) that the CRT got a heater. Electronic TV using a CRT with photo target as camera as well as display was proposed about 1906. Baird was very steam punk with his mechanical TV based on Victorian era Nipkow Television.
The Disk mechanical TV is limited to under 30 lines! or about 12 readable characters. Using stacked plates as a set of 200 to 300 mirrors (the plate edges) then about 20 wide by 20 high text is just about possible.
Aconite (?) gas lamp illumination and mechanical drive is possible. But it has no memory and needs refresh of at least 11 fps. The static beads, hinged mirrors or flip panels all have memory and the beads and panels use ambient light.