Denier - Charlemagne Mainz, monogram

The monogram denier was the direct product of Charlemagne's monetary reform of 793–794, which scrapped the lighter Merovingian standard and imposed a heavier silver penny across the Frankish realm — one of the most sweeping currency unifications medieval Europe would see. Mainz, as a major ecclesiastical and commercial hub on the Rhine, was among the mints authorized to strike the new type. The reform tied coin weight to a redefined pound standard, and enforcement was serious: capitularies threatened punishment for any mint or merchant dealing in underweight pieces.