(Container) of silverblack

(wondrous item, rare)

This glass vial holds silvery liquid with a faint odor of iron to it. If applied to a non-magical metallic weapon by a blacksmith, it will make that weapon a silvered weapon permanently. Each vial can cover one Medium-sized weapon or 20 arrow/bolt heads.

Knowledge of how to create silverblack is quite rare, and most smiths would be willing to pay 500gp (or more) for a vial.