A pair of stamps issued by the Republic of Chad in 1969 commemorated the travels of two German explorers of the continent of Africa.
The right-hand stamp has a portrait of 19th century German explorer Heinrich Barth (1821-1865) next to Lake Chad. Barth was one of the first Europeans to recognise the significance and richness of African history and culture. Travelling under the Arabic name Abd el Kerim, he crossed the Sahara desert and over the Air mountains into Central Africa.
However, the stamp error is contained in the stamp on the left which shows Gustav Nachtigal (1834-85). The son of a Lutheran pastor from the town of Eichstedt in Saxony-Anhalt, Nachtigal trained as a doctor and for several years practised as a military surgeon in Cologne. After contracting a severe lung disease, in October 1862 he moved to Bona (present-day Annaba), Algeria, hoping to regain his health in the warm, dry climate. The following year he settled in Tunis, where he lived for several years, practised medicine, and learned Arabic. He was about to return to Germany when he was asked, by another German explorer, Gerhard Rohlfs, to undertake a mission to the kingdom of Bornu in the northern part of present-day Nigeria, on behalf of King William I of Prussia. William wanted to thank the sultan of Bornu for the kindnesses he had shown to Heinrich Barth during a previous expedition.
Nachtigal accepted the assignment and in February 1869 set out across the Sahara with six men and eight camels. The first part of the journey was from Tripoli (present-day Libya), through Fezzan in south-western Libya and the region of Tibesti (parts of present-day Libya, Chad, and Niger) to Bornu, where he presented gifts from the Prussian king to the sultan. He then travelled from Bornu to the sultanate of Baguirmi (present-day Chad) and to Timbuktu (present-day Mali). The expedition carried on from Wadai (now in eastern Chad), through Darfur (present-day Sudan), and on to the Nile at Khartoum. In all, Nachtigal covered nearly 10,000 kilometres, travelling to parts of Africa never previously visited by any European. He ranks as one of the greatest European explorers of the African continent.
Back to the stamp error! To celebrate a visit by the then German Federal President Dr. Heinrich Lübke to Chad, in 1969 the Republic issued an airmail stamp to honour the achievements of Gustav Nachtigal.
On the Nachtigal stamp you can see a staff, or rod, entwined with two serpents. This was meant to represent the Staff of Asclepius, a Greco-Roman god associated with healing and medicinal arts. But the stamp’s designer mistakenly added a second serpent on the staff.
The staff with two serpents, known as the caduceus, is particularly inappropriate for use as a medical symbol due to its long associations with the Greek god Hermes, who was patron of commerce and traders as well as thieves, liars, and gamblers.