A while back I got part of a communication console unit that was ex military. Not being able to find anything on it at the time I later found out it was part of the desk consoles used for Air Traffic Control for the RAF. I later bought two more units that were slightly different as the previous unit had some useful MM5450N constant current LED driver chips in them which could be salvaged for Arduino projects. These chips are basically a chain of shift registers so could easily be used for driving a 4 digit LED display.
I thought I’d post the videos of the teardowns if anyone is interested.
Video of the two later units