How many Disc systems from the eighties and earlier now cant be read?

Its not just the media its keeping a device which can play them.

Many companies and of course public organsations backed everything to laserdisk.

I remeber as a kid the BBC computers at work had these ultra expensive laser disks systems for the doomsday project i belive now its almost impossible to read the format.
The orginal Doomsday book can still be read.