Obsidian and Moonstone (3.5e Equipment)
From D&D Wiki
These dual masterwork gunblades always come in a pair, one made from obsidian and moonsteel, the other from moonstone and doomsteel. They are so perfectly built that they almost never jam. They were crafted on The Clockwork Nirvana of Mechanus alongside 200 other sets, it is unknown how they sets of guns were spread throughout the planes but it appears they are of little consequence to the Inevitables who reside there.