Commemorative Envelope 1963 Greece World Jamboree Boy Scouts

First day cover from Greece from 1963, issued on the occasion of the 11th World Boy Scout Jamboree.
The 11th World Scout Jamboree took place at Lake Marathon in Greece.
The Greek postal service issued a series of five special stamps for the occasion, which went into circulation on August 1.
The stamps feature various motifs, including:
The badge of the 11th World Jamboree.
The Greek Crown Prince Constantine, who co-organized the Jamboree.
A drawing of the Acropolis at sunrise, painted by Lord Baden-Powell, founder of the Scout Movement.
The founder of the Greek Scout Movement, A. Lefkaditis, together with Lord Baden-Powell.
A Scout blowing a conch shell.