The “Illyrian” (or “Greco-Illyrian”) style helmet was made by the Greeks in the Peloponnese during the 8th and 7th centuries BC (Connolly, 60). Inspired by the Kegelhelm, this helmet was made out of bronze, and covered the head differently, depending on the type of helmet. There were four different types of Illyrian helmets. The Type I Illyrian Helmet impaired hearing, and gave no neck protection, by type IV, the helmet offered plenty of neck protection, and did not impair hearing at all (Treister).
Connolly, Peter. Greece and Rome at War. London: Greenhill ;, 1998. Print.
Treister, Michail Yu. The Role of Metals in Ancient Greek History. Leiden: E.J. Brill, 1996. Print.