The sitter was the fourth son of Ferdinand Albert II, Duke of Brunswick-Lüneburg and Antoinette Amalie of Brunswick-Wolfenbüttel. A successful Field-Marshal, during the Seven Years' War, he repelled attempts by the French to occupy Hanover.
A replica in identical frame is described and illustrated in Stefanie K. Werner's exhibition catalogue Miniaturen: Große Malerei auf kleiner Fläche, Brunswick, Herzog Anton Ulrich-Museum, Burg Dankwarderode, 2010, pp. 40-41, no. 13.
Two slightly later miniatures of the present sitter are illustrated in K. Schaffers-Bodenhausen and M. Tiethoff-Spliethoff, The Portrait Miniatures in the Collections of the House of Orange-Nassau, Zwolle, 1993, p. 253, nos. 273-274.