The main RuneScape Wiki has an article on: Mithril Chain Mail Body
The Old School RuneScape Wiki also has an article on Mithril Chain Mail Body.

A Mithril Chain Mail Body is a type of chain mail body which can be worn by players with at least level 20 defense. It can be smithed from three mithril bars by players with at least level 61 smithing, granting 150 smithing experience. It can also be purchased from Horvik's Armour Shop and Wayne's Chains.

Dropped by

Monster Combat level Quantity Rarity
Lesser Demon 79 1 4Rare

Bonuses

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