Denier - John VIII and emperor Louis II

This denier was struck during one of the few instances of explicit co-authority between pope and emperor formalized on coinage, a political arrangement born from John VIII's acute need for Carolingian military protection against Saracen raids that were devastating the Italian peninsula in the early 870s. Louis II had spent years campaigning in southern Italy — he took Bari from the Arabs in 871 — and the papal mint's acknowledgment of his authority was as much a diplomatic instrument as a monetary one.

Louis died in August 875, collapsing the arrangement abruptly and ending what remains one of the shortest jointly-issued papal-imperial series on record.