Punched inscription on the neck guard reads: "VI.HIR.#.FIRON.PI" The beginning of the inscription VI probably marks a warship, in fact a 'six' Hexeris; its abridged name (partially corroded away) HIR perhaps can be read as "Hirundo" = 'swallow'. The following sign, that looks approximately like a double fish-hook (#), is maybe to be read as anchors. The following 'Firon' or 'Piron' then would be the name of a marine. The last two letters could be to be interpreted as 'Publii libertus' (?). The ship probably belonged to the transportation fleet consisting of 1000 units, that were assembled by Germanicus for the campaign of 16 AD. (Tacitus, Ann. 2,6), and that had an accident on the journey home in the storm before the Dutch coast (Tacitus Ann. 2, 23.24.)
Oval hemispherical, heavy helmet bowl with gently sloping neck guard, and a strongly thickened forehead edge and soldered, conical plume holder.
References:
Robinson, H.R. (1975), "The Armour of Imperial Rome", (Arms & Armour Press), p.34, Nos.66-68
Klumbach, H. (1974), "Römische Helme aus Niedergermanien", (Rheinland-Verlag GMBH Köln), p.34, Taf.25