 More is known about Celtic Normandy due to the archeological sources being more numerous and easier to date.As early as the 19th century, local scholars studied archeological sites (especially those of Upper Normandy) and recorded their discoveries.They discovered objects such as the Gallic gilded helmet of Amfreville-sous-les-Monts, made in the 4th century BC, and the iron helmet currently in the Museum of Louviers.