Ernestine duchies
Altenburg went to the Duke of Saxe-Hildburghausen, but he gave Hildburghausen to the Duke of Saxe-Meiningen-Hildburghausen.  The duke of Saxe-Coburg-Saalfeld gave up Saalfeld in return for Gotha.. All of the Ernestine Duchies ended with the abolition of the monarchy and princely states in Germany shortly after the end of World War I.