Denier with square shield - John I

John I ruled Brittany for nearly five decades, and his coinage reflects a reign long enough to produce substantial die variation across multiple phases of production. The denier references cluster around mid-13th century monetary reforms in the French feudal system, when regional lords were under increasing pressure from the Capetian crown to standardize — and in some cases surrender — their minting rights. John resisted this encroachment longer than most of his contemporaries.

The square shield type is catalogued distinctly from John's other denier issues precisely because of heraldic specificity in die execution, not mere design whim.