User blog comment:LOTRMod/On the Removal of Diamonds/@comment-25012056-20141230123044/@comment-50.36.65.10-20141231172707

Yes, the helms of the Tower Guard were made of Mithril. However, most of Gondor's forces did not have Mithril. The Tower Guard were the elite brigade, basically, and had Mithril helms from the days of old, most likely the days of Elendil the Tall and Isildur. They would have been supplied by the Dwarves, or perhaps the Elves who acquired Mithril from the Dwarves. But it should be craft-able on Gondor's crafting tables, as no other nation has these helms, even if they were probably not Gondorian in origin.