Denier - Nicholas I and emperor Louis II

This joint issue reflects one of the more awkward political arrangements of the Carolingian period. Nicholas I, elected pope in 858, cultivated an assertive conception of papal authority that brought him into repeated conflict with secular rulers — yet this coinage advertises a cooperative relationship with Louis II, the Carolingian emperor who controlled Italy and on whose military protection Rome depended. The pairing was less a partnership than a mutual necessity: Nicholas needed Louis's armies; Louis needed papal legitimacy.

The type is among the earliest coins attributable to the papal mint at Rome operating under documented joint imperial-papal authority.