John VIII was the son of emperor Manuel Palaiologos and the penultimate emperor of Byzantium. He is also the final emperor represented in the seals collection at Dumbarton Oaks. The empire that John ruled was but a shadow of its former self. Two years before he came to the throne, Thessaloniki had been given to the Venetians in the hope of saving it from the Ottomans. Elsewhere John ruled a little of Thrace, a few islands, the city of Constantinople, and the Morea. This southern province was had become a flourishing hub of Byzantine culture, centered around the court of the despots in the city of Mystras. John's brother Constantine had even managed to expand his little realm by conquering the remainder of the Morea and Attica. John spent much of his reign attempting to gain aid against the Ottomans from the West. John travelled to Venice and Hungary in 1423–24 to ask for aid in person. In 1438 a Byzantine delegation, led by the emperor, arrived in Venice, on their way to attend a council of the Church in Ferrara. Later the council moved to Florence and it was here, in 1439, that John signed an act of union formally placing the Byzantine church under the jurisdiction of the pope. It was John's hope that by this act he would benefit from a Western crusade against the Ottomans which would save his crumbling empire. The resulting crusade was crushed at Varna in 1444, and with it died the last real hope Byzantium had of attaining aid from Western Europe. John died in 1448 preceding his empire by just five years.
This golden seal of John VIII displays Christ before a low throne on the obverse, and the emperor, wearing a crown and loros, holding a long cross and an akakia on the reverse. John is identified as autokrator, the only appearance of a title other than despotes on an imperial seal since the reign of Michael VII (1071–1078).