Papal armorial

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), in reference to :
The gold key signifies that the power reaches to heaven and the silver key that it extends to all the faithful on earth, the interlacing indicating the linking between the two aspects of the power, and the arrangement with the handles of the keys at the base symbolizes that the power is in the hands of the pope.
The oldest known representation of the crossed keys beneath the papal tiara in the Coats of arms of the Holy See dates from the time of Pope Martin V (1417–1431). His successor Pope Eugene IV (1431–1447) included it in the design of a silver coin.
Martin V also included the keys in his personal arms (those of the Colonna family); however he did not show them as external ornaments, instead placing them in chief on the shield (this example was followed by Urban V and VIII and Alexander VII; Nicolas V seems to have used just the crossed keys and the tiara in an escutcheon. The placing of the keys above the shield becomes the fashion in the early 16th century, so shown on the tomb of Pius III (d. 1503). Adrian VI (1522/3) placed the keys in saltire behind the shield.
High Middle Ages.
Heraldry developed out of military insignia from the time of the First Crusade. 
The first papal coats of arms appeared when heraldry began to be codified in the 12th to 13th centuries. 
At first, the popes simply used the secular coat of arms of their family. 
Thus, Innocent IV (1243-1254), who was born Sinibaldo Fieschi, presumably used the Fieschi coat of arms, as did Adrian V (Ottobon de Fieschi), the nephew of Innocent IV.
According to Michel Pastoureau, Innocent IV (1243-1254) is likely the first who displayed personal arms, but the first of whom a contemporary coat of arms survives is Boniface VIII (1294-1303).
Modern sources show attributed arms of the popes of the second half of the 12th century; thus, editions of the "Annuario Pontificio" of the 1960s presented the arms of the popes beginning with Innocent III (1198-1216), and John Woodward gave those of the popes from Lucius II (1144-1145) onward, though he noted that "it seems probably that many of the early popes made little if any use of their family arms".
Thus, Innocent III (Lothaire de Segni, 1160–1216) and Gregory IX (Ugolin de Segni, 1145–1241) may have used the coat of arms of the counts of Segni.
The following papal coat of arms should be considered "traditional", lacking contemporary attribution. 
For the popes of noble families, the coats of arms of the family is substituted, and for commoners, the traditional coat of arms as shown in early modern heraldic sources.
Late Middle Ages and Renaissance.
Note that some of the images of the coats of arms shown below anachronistically include the external adornments of the papal tiara and the keys of Peter. These ornaments were not in use before the 1450s.
Popes of the Early Modern period.
Most popes of the 16th to 18th centuries came from Italian noble families, but there were some exceptions, such as
Sixtus V (1585-1590), who was of low birth.
Popes of the modern period.
The last person elected as pope who was not already an ordained priest or monk was Leo X (Giovanni di Lorenzo de' Medici) in 1513. Thus, throughout the Early Modern period, the elected pope already had a coat of arms: if he did not have a family coat of arms to begin with, he would have adopted one upon being made bishop. Upon his election as pope, he would continue using his pre-existing coat of arms, in some cases with heraldic augmentations. This tradition was continued into the modern period.