Doing a bit of googling on this subject I came acoss a
german, Prof Karolus.
A search of this forum did not show Karolus so maybe many here are not familiar with this display which is 5 times the size of Baird's

Date is 1935. I cannot find how it was switched but valves are used.
100 channels, nine valves per channel.
Write up and a possible photo of the 2m x 2m screen attached.