Denier Tournois - John IV Nantes

John IV spent much of his reign navigating between English alliance and French pressure — he had been raised at the English court and returned to Brittany with English military backing in 1379 after years in exile. The denier tournois coinage he issued drew directly from the French royal tournois tradition, a deliberate monetary mimicry that kept his currency legible across a duchy whose trade ran in both directions.

The tournois type had been the workhorse of French petty commerce since Louis IX's reforms at Saint-Martin de Tours in the thirteenth century. That John IV continued striking in this idiom rather than asserting a distinctly Breton form says something about the practical limits of ducal independence.