These plaques are executed in the style of Jacques Laudin (1627-1695), who along with his son, executed several series of portrait medallions of the Twelve Caesars, after engravings by Marcantonio Raimondi. Examples of these enamels can be found in the Louvre and also in the former Reculis collection. Laudin's son, also named Jacques carried on his fathers work into the begining of the 18th century.
Philippe Verdier, Catalogue of the Painted Enamels of the Renaissance, The Walters Art Gallery, Baltimore 1967, nos. 207-208, p.389.
Susan L. Caroselli, The Painted Enamels of Limoges, Los Angeles County Museum of Art, 1993.