Portrait of Roman Emperor Caracalla; inscription in Greek letters O IIETPOC and cross added at the Byzantine period in order to transform the portrait in that of St. Peter. Amethyst intaglio, ca. 212 AD. From the treasury of the Sainte-Chapelle in Paris, BnF Museum [664×908]

Portrait of Roman Emperor Caracalla; inscription in Greek letters O IIETPOC and cross added at the Byzantine period in order to transform the portrait in that of St. Peter. Amethyst intaglio, ca. 212 AD. From the treasury of the Sainte-Chapelle in Paris, BnF Museum [664×908]

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