Niello /(?)/

Ni·el·lo

Niello

n.
  1. A metallic alloy of a deep black color.
  2. The art, process, or method of decorating metal with incised designs filled with the black alloy.
  3. A piece of metal, or any other object, so decorated.
  4. An impression on paper taken from an ancient incised decoration or metal plate.
  5. An impression on paper taken from the engraved or incised surface before the niello alloy has been inlaid.