Papal coats of arms are the personal coat of arms of popes of the Catholic Church. These have been a tradition since the Late Middle Ages, and has displayed his own, initially that of his family, and thus not unique to himself alone, but in some cases composed by him with symbols referring to his past or his aspirations. This personal coat of arms coexists with that of the Holy See. Although Boniface VIII (1294–1303), Eugene IV (1431–1447), Adrian VI (1522–1523) and a few others used no crest above their escutcheon, from John XXII (1316–1334) onward the papal tiara began to appear (a custom maintained until Nicholas V) and, from the time of Nicholas V's successor, Callistus III (1455–1458), the tiara combined with the keys of Peter. Even before the early modern period, a man who did not have a family coat of arms would assume one upon becoming a bishop, as men did when knighted or on achieving some other prominence. Some who already had an episcopal coat of arms altered it on being elected to the papal throne. The last pope who was elected without already being a bishop was Gregory XVI in 1831 and the last who was not even a priest when elected was Leo X in 1513. In the 16th and 17th century, heraldists also made up coats of arms for earlier popes, especially of the 11th and 12th centuries. This became more restrained by the end of the 17th century. External ornaments Papal coats of arms are traditionally shown with an image of the papal tiara and the keys of Peter as an external ornament of the escutcheon. The tiara is usually set above the escutcheon, while the keys are in saltire, passing behind it (formerly also en cimier, below the tiara and above the shield). In modern times, the dexter and sinister keys are usually shown in gold (or) and silver (argent), respectively. The first depiction of a tiara, still with a single coronet, in connection with papal arms, is on the tomb of Boniface VIII (d. 1303) in the Archbasilica of Saint John Lateran. Benedict XVI in 2005 deviated from tradition in replacing the tiara with the mitre and pallium (see Coat of arms of Pope Benedict XVI). The two keys have been given the interpretation of representing the power to bind and to loose on earth (silver) and in heaven (gold),