Saxe-Saalfeld
The Duchy of Saxe-Saalfeld was one of the Saxon Duchies held by the Ernestine line of the Wettin Dynasty. Established in 1680 for Johann Ernst, seventh son of Ernest I, Duke of Saxe-Gotha. It remained under this name until 1699, when Albert, Duke of Saxe-Coburg died without sons. His brother Johann Ernst of Saxe-Saalfeld became the new Duke of Coburg and the duchy was renamed into Saxe-Coburg-Saalfeld in 1735.
Read more about Saxe-Saalfeld: Dukes of Saxe-Saalfeld