 The title "Grand Master" is applied retrospectively; the medieval heads of the order took the title of "custos" ("guardian") of the hospital.The title "magister" ("master") is used on coins minted in Rhodes, beginning with Foulques de Villaret.The first to use the title "Grandis Magister" ("Grand Master") was Jean de Lastic (r. 1437–1454); the title "Grandis Magister" is found on coins minted by Pierre d'Aubusson (r. 1476–1503).