Republic of Viet-Nam Air Force (VNAF) - Recruiting
Figure 3. July 1966 cover with VNAF recruiting slogan.
From its inception until the collapse of the Republic of Viet-Nam in April 1975, the VNAF operated as an all-volunteer air force. In 1966, a concerted recruiting campaign was undertaken as evidenced by various slogans found on covers from that period. These slogans were apparently applied by the civilian post office, not the military postal service; none of the examples I have seen bear a "Quan Buu" military postmark. Figure 3 shows a July 1966 cover with a hand-stamped slogan that translates as, "Celebrating the Air Force Festival. Join the Air Force. Protect the Air Space of Viet-Nam."