Note: Do not rely on this information. It is very old.
Altenburg
Altenburg, The Duchy of Saxe-Altenbueg, situated between the kingdoms of Prussia and Saxony, the principalities of Reuss, Schwartzburg, and Coburg, and the grand duchy of Weimar, held by a branch of the Saxe-Gotha family until 1825, when it became incorporated in the German Confederation, and subsequently in the empire.