1 Piastra - Antonio Barberini Sede Vacante

Sede Vacante issues were struck during the interregnum between papal reigns, administered by the Camerlengo of the Holy Roman Church — the cardinal responsible for confirming the pope's death and governing temporal affairs until a successor was elected. In 1655, that office was held by Antonio Barberini the Younger, nephew of Urban VIII, whose family's political fortunes had collapsed after his uncle's death in 1644 sent the Barberini into French exile under threat of prosecution by the Pamphilj faction.

The conclave of 1655 elected Fabio Chigi as Alexander VII after eighty days of deliberation.