For "London Underground Medium", it's almost certain this technology is character based (it's not archaic enough to be hand-crafted values) and so somebody with even test access to a 1996 stock (ie Jubilee Line trains) can presumably tell one to display notices with the desired characters: F K Qq U V X Y Z and take a photo without it ever being in service.

On the other hand, the 1995 stock is very similar, same vendor, same era, likely identical display panels so I'd expect you could collect some of this data (e.g. London Zoo is accessed via the Northern Line, and that's a Z right there if the display mentions this) from those trains and assume it's the same.