I recently purchased two cinderellas which have their designs and colours based on Sudan's Camel Postman postage stamps, as illustrated below:

They are inscribed "Für die katholische Mission Khartoum" and they have an imprint reading "Missionsprokurator: Augsburg, Sonnenstr 4", so they seem to have been issued by German Catholic missionaries. One of the stamps seems to depict missionaries in Sudan while the other shows the flight into Egypt ("Jesus in Aegypten").
Has anyone seen these cinderellas before, and does anyone have any information about them? It would be interesting to know their date of issue, whether there are other similar cinderellas, whether they were used in Germany or in Sudan etc.