Very beautiful helmets of the Gallic Celtic period, few of them have been found to date.

From Normandy to Charente, two of the beautiful ceremonial helmets of the Gallic Celtic era.

The ceremonial Helmet of Amfreville found in Amfreville-sous-les-Monts, Normandy, North-West of France, dated from – 250 BC.

Made with gold, bronze, iron and enamel. White or pink gold has corroded, only the purest gold parts remain. |
Dimensions: 23 centimetres (9.1 inches) , 16.5 centimetres (6.5 inches) long and 16 centimetres (6.2 inches) deep.

In addition, here is a 3D rendering:

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Moreover, the ceremonial Helmet of Agris is a bit older, found in West of France, dated from -400 to -350 BC.

Made of an iron hull, with bronze ornamental strips and a decoration in light relief, entirely covered with 99% pure gold leaf, as well as many corals circling the circumference of the helmet and the cap.
Dimensions: 21.4 centimetres (8.4 in) high, 23 by 19 centimetres (9.1 by 7.5 in) wide. Cheek-guard: 9.4 by 7.6 centimetres (3.7 by 3.0 in).

Similarly, here is a 3D modeling on sketchfab

The ceremonial helmet of Agris, in current Charente, -400 to -350 BC (Musée des beaux-arts, Angoulême) |
Coll. du Musée d’Angoulème by DIGISCAN3D, on Sketchfab.

After that you can find a blog post entirely on this topic here (in french) with graphics from this item itself.

Also an equally interesting article on this subject (in french), published in the CNRS Journal from July-August 2010. [.pdf version here (in french)]

In conclusion, you will find another item in this tweet

Sanglier de Soulac-sur-Mer (Gironde) #Gaulois #Celts #art #bronze
Cette sculpture en bronze date de l’époque de la Tène (450-25 av JC). Cet objet est une enseigne militaire. Pour les gaulois, le sanglier était un animal sacré. pic.twitter.com/ZVbuUiOaXB

— 🦓Dominique Hoffman🖋️ (@zebras54) June 3, 2019

You could be also interested by this post Sanxay Gallo-Roman site