The masking tape note that states which aircraft's inventory the headset was part of.
This "low impedance" HS-33 (ANB-H-1) headset, possibly previously used on e.g. P-51 and AT-6 in its original version, was modified for use on post-war aircraft.
In particular, according to the note written on the masking tape applied to the headset, this assy was part of the Pilatus P.3 tail number A-829 inventory. (masking tape probably applied when the headset phased out to be replaced by the more modern
Instead of the usual banana mount on which to fix the M6A-UR microphone, the HB-7 mount was modifiied by fitting a small junction box in order to connect a laryngophone (usually a T-30) PL-291 socket and the installation of a section of British G-Type comm harness (the standard of the time given the aircraft operated by the SAF); The P.3 had the same airframe side comm system fitted.