2909964 ✉ 1976 6c Gemstone on commercial airmail cover (opened out) from Navy Office, ACT to UK with fine strike of boxed 'NAVY POSTAGE/CONCESSION RATE'. Sender was R.N. Commander.
3111438 ✉ 1976 (Apr 7) British Defence Forces Mail concession rate cover to London with 6c Gemstone tied by Townsville Military PO '7AP76' datestamp. Rare usage.