While absolute dating has become the archaeological gold standard, typology can provide context beyond time frames. Here, the authors demonstrate this with the chronological assessment of iron helmets from the underwater site of Piedras de la Barbada, near Benicarló (eastern Spain). Marine concretions helped preserve fabric linings in several helmets, permitting direct radiocarbon dating of the assemblage to the late fourteenth or early fifteenth centuries AD. Typological and iconographic comparisons agree, identifying the helmets as regionally produced, light-infantry equipment that pre-dates the fifteenth-century standardisation of European plate armour systems, corresponding with a period of maritime insecurity along the Valencian coast.