Sacu

As the world`s oldest custom union, the Southern African Customs Union (SACU) dates back to the 1889 Customs Union Convention between the British Colony of Cape of Good Hope and the Orange Free State Boer Republic. A new agreement, signed on June 29, 1910, was extended to the Union of South Africa and the British High Commission Territories (HCTs), i.e. Basutoland (Lesotho), Bechuanaland (Botswana), and Swaziland, South West Africa (Namibia) "was a de facto member, since it was administered as part of South Africa" before it became a dejure member. The primary goal was to promote economic development through regional coordination of trade.