Tibetan helmet, of a type used from the 8th – 16th centuries. Helmet skull made of eight plates laced together with leather, with an attached skirt formed from the type of lamellar known as “willow leaf.” Surprisingly well-preserved examples of these helmets still exist in Tibetan monasteries, having been acquired and maintained by the priesthood from warriors who took vows.
Flexibility imparts no advantage to a helmet, which is intended to prevent penetration and diffuse force over as wide an area as possible, so riveting the same plates makes a better helmet than lacing them, by improving rigidity. However, riveting brittle natural materials like boar's tusk or cow's horn works poorly, because the material usually fails under the compression of the rivet. Lamellar armour made from iron is merely an extension of this earlier technology, replacing hardened leather, tusk, etc. with iron plates. The practicality of lacing made more sense with the earlier materials, but remained as a relic until more appropriate techniques were developed to deal with improved materials.
The Metropolitan Museum of Art, in New York, has a more extensive collection of this sort of armour than any other institution that I am aware of. In recent years they had a special exhibit on Tibetan warriors, along with a published catalogue. I also have some digital images in my research library, which I will give to you if you send me your email by private message.
The only weight I have for an original is only of the skull, which is just over one kilogram. My entire helmet is just over two kilograms, which leads me to believe that I used a similar thickness of metal to the original.