for sure this flex cable will send commands from the front panel to the meter circuit, say in a master slave configuration ...
remove the front panel, the meter will stay dumb ...
some reported in the past some zenner failures and or capacitors failures, on the front panel pcb ....
if you have the old unobtanium nec vfd drivers, they may or will leak on the vfd segments over time ... wich mean the meter can not be repaired on the front panel
if you have the latest vfd board you're lucky
normally you had some Hp Agilent notes about the front panel board vs the serial numbers, and FW versions