Going by Burkhart-san’s deduction there is a orichalcum plating spread out underneath the mithril plating.
Something like a composite plating of mithril and orichalcum.
In case of this setting being shown in a robot anime in my previous life, it might be interesting, but it was nothing else but a source of trouble if this was your enemy.
“However, it is a bothersome, overly-strong, strategic weapon.” (Wendelin)
But even then, it was still preferable to a tactical weapon.