The earliest group of Roman helmets were the Montefortino helmets, named after the first major find site. These types of Roman helmets were worn by the Republican consular armies. The helmets dated from the 4th century BC to the 1st century AD. Made from brass, domed shape, the Montefortino helms had a small extension at the back as a neck guard. They normally had a plume holder on the top of the helmet.
The next group of Roman helmets, the Coolus helmets, were based on a Gallic form of helmet made in the Coolus district of Marne. This group of Roman helmets covered the period from the 3rd century BC to around 79AD. These simple Roman helms consisted of a hemispherical bowl made from bronze and had a reinforcing peak that ran horizontally across the brow and had a larger extension in the back as a neck guard. Many of the Roman Coolus helmets had a simple top spike as a plume or crest holder.