22 July 1958
The first country (or set of countries) is also the most strange one: on the official EXPO 58 cover, you will notice National Day of Egypt, but the National Day was of Union of Arabian Countries.
These Union of Arabian countries built a building which housed four countries: Egypt, Syria, Jordan and Irak.
The Union itself was the youngest created at that time: February 1958, and was formed by Egypt and Syria.
The only happening, except the exposition of the buidling to the public, was a reception held at 18.00 the Grand Auditorium on 22 July 1958.
Official Expo 58 cover edited by Campo Rodan
The Official edited cover with logo of the Union (edition is not identified).
A private cover with all Belgian stamps cancelled.
A egicarte cancelled