The Imperial Gallic I helmet
At the end of the Imperial Gallic series of helmet types (a.k.a. Weisenau-type, in the continental style), there's a small set of copper-alloy helmets. H.Russell Robinson called these helmets the type "I". In fact, to be completely honest, at the time he wrote his influential The armour of Imperial Rome that plural was due to one helmet bowl, from Mainz, and two cheek-pieces, from Nijmegen and Caerleon, which Robinson determined to be an appropriate fit.
As far as I can see, at least three more helmets of this type have been found and identified since Robinson's book was published in 1975. At this point, I should point out that Robinson's typology has received quite some criticism because of the focus on narrow design features, often based (as here) on a very limited set of samples. The group of helmets discussed here all share the fact that they're made of a bronze alloy, with bronze alloy appliques, they have crest or feather holders on the side, a crest knob (or mounting) and 'eyebrows'.
The first new find used to belong to the Axel Guttmann collection, which was sold at auction over a decade ago. I have no information about its provenance, and it's apparently in a private collection now, but perhaps someone else does? The second is now in the Aquincum Museum (Hungary, same link as before), a possible third, also shown at Romancoins.info, may belong to this group as well and is reportedly from the Po river near Cremona and related to the Year of the Four Emperors. The fourth, finally, is/was in the collection of the now-closed Museum Dorestad in Wijk bij Duurstede (NL) and is depicted here.
Like the Mainz helmet and the one from the Guttmann collection, this helmet has an ownership inscription. It was used successively by Titus Allienus Martial(n)is and Statorius Tertius, both of the centuria of Antonius Fronto. Now, those names sound distinctly Roman, and they are likely Roman citizens. So it could be, as has been supposed, that these three men were all members of the well-known Cohors XV Civium Romanorum Voluntariorum which is known to have operated along the Lower Rhine in the Netherlands. The helmet, however, was found in Rijswijk, on the south side of the, granted meandering, Rhine, barely 15km from the Batavian settlement at Tiel-Passewaaij.
Date and attribution
I promise I'm not purposely writing only blogs about topics that have some remote relation with the Roman imperial fleets, but... It appears this one might fit that category as well. The very first helmet in this series has extensive owner inscriptions: it belonged to Lucius Lucretius Celeris of Legio I Adiutrix. This legion had of course been established as a Iusta legio by Galba from troops of the Classis Misenatis in AD 69, and then fought for Otho at the first battle of Bedriacum before coming north to help defeat the Batavian revolt. It was then based in Mainz until the mid 80s, when it moved east to Brigetio (modern Szőny, Hungary) in Pannonia.
Its sister legion, II Adiutrix, raised from troops of the Classis Misenatis, in AD 70, also helped put down the Batavian revolt, then went to Britannia until the end of Agricola's tenure as governor. It too then went east, fought in the various Dacian campaigns and found a home in Aquincum, Pannonia. There the heirs of Caius Castricius Victor, soldier of II Adiutrix, had a memorial set up for their comrade. On it, he is depicted wearing a helmet with what has been suggested are horns. Might they instead be feathers?
Perhaps I'm taking things too far, but the pattern seems to suggest the Legiones Adiutrices may have been equipped with Imperial-Gallic style helmets, entirely made of a copper alloy, which they took with them when they went to fight the Batavians and then possibly into England (though Caerleon is some distance from where II Adiutrix is known to have been), and east to Pannonia.
Did I drink too much last night? Unfortunately, this doesn't match with the 'fish-eyebrow' helmets and the reconstruction of a legionary of I Adiutrix by Mike Bishop and Graham Sumner in issue XII.4...