Some of the helmets that appear in the archaeology are quite superb.

Shown here is an example from Agris (Charente)
It is made of iron, with bronze plates attached. Plated with gold and then inlayed with pearl and coral. The rivets are silver. It has an internal fitting of wood and leather.
It dates to 4th century BC.

The other helmet that is associated with the Celts, is from Britain. It is known as the Batesea Helmet, and was found it the River Thames. It dates to 1st century AD, and is too small to be worn. It is therefore thought to be an offering, specially made.