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

A Black Chain Mail Body is a chain mail body which requires level 10 Defense to equip. It can be bought from Wayne in Falador or obtained through monster drops. As with all other black armour, this item cannot be made with the Smithing skill.