The ear guards and the border across the bow were raised out of the helmet skull.
Ball-headed rivets were used to secure the frontal peak and cross-skull reinforcements, rather than the conical type. The same rivet was used to secure the front of the back-to-front bar as well as the centre of the peak.
The edges of the neck guards have been notched to retain the edge binding.
References:
Robinson, H.R. (1975), "The Armour of Imperial Rome", (Arms & Armour Press), p.98, No.263-5, 2
Klumbach, H., (1974), "Römische Helme aus Niedergermanien", (Bonn), p.43 & Taf.30, 1
