Sources about the Roxolani/ leather armour

[Nathan Ross]

That passage doesn't say anything about hardened leather.

Doesn't praeduro corio literally mean 'hardened leather'? Rawhide would be corio crudo.

You could interpret the phrase as a reference to hide, and you would probably be right, but Tacitus isn't specific in the text.

Pausanius and Ammianus also mention Sarmatian armour made from horses' hooves. That may have been a myth, or a literary trope of some sort, but we perhaps shouldn't be too exclusive of other possibilities.