I offer a cover : Royal Tournament Earls Court London.  26th July 1968.  British Forces Postal Service 1068.  1/- Royal Air Force Stamp. 

Size: 162mm x 114mm.

Cover Publisher: Royal Engineers Postal Service to HM Forces.

Condition: Very good.

All covers are sent in a protective sleeve with card protection.  I will combine postage on multiple purchases - please wait for my invoice.