Sources about the Roxolani/ leather armour

[Dan Howard]

That passage doesn't say anything about hardened leather. A better translation would be something like "plates of iron or very tough hides". The vast majority of armour made from animal skins all over the world was rawhide, not leather. The vast majority of armour made from hide was scale armour. Leather/rawhide armour weighs MORE than metal armour. The whole point of going to the trouble and expense of using metal to make armour is that it was the lightest material available.