There is only one enamel signed and dated (1555) by Jean de Court, who was active between 1553 and 1585. It is a portrait of Marguerite de France, daughter of François I and wife of Emmanuel Philibert de Savoy, in the guise of Minerva. Features from this portrait are found again in an oval plaque of Minerva which is signed I.D.C., and these initials are the basis for Court's other designation as Master I.C.
It is likely that the enameler Jean de Court, who signed his works I.D.C. and initialed workshop pieces I.C. (occasionally C.I.), was the same person as Jean de Court, who, having been painter to prince de la Roche-sur-Yon in 1553, became painter in 1562 to Mary Stuart, the consort of King François II. In 1572 Court succeeded François Clouet as painter to Charles IX. Like Léonhard Limousin, he may have lived at the French court while directing an enameling workshop in Limoges. [This is an edited version of the artist's biography published, or to be published, in the NGA Systematic Catalogue]
Ardant, Maurice. "Emailleurs limousins: Jehan court dit Vigier, Susanne Court, Jean de Court." Bulletin de la société archéologique et historique du Limousin 11 (1861): 5-21 19-21.
Edited by Ulrich Thieme and Felix Becker. Allgemeines Lexikon der bildenden Künstler von der Antike bis zur Gegenwart, 7:583-584.
Verdier 1967, xxv-xxvi.
Distelberger, Rudolf, Alison Luchs, Philippe Verdier, and Timonthy H. Wilson. Western Decorative Arts, Part I: Medieval, Renaissance, and Historicizing Styles including Metalwork, Enamels, and Ceramics. The Collections of the National Gallery of Art Systematic Catalogue. Washington, D.C., 1993: 97.