Copper, zinc, and tin have been used in combination for at least two thousand years. Together, these three alloys make a single metal of superior strength. People began calling it “gunmetal” after it was used to build cannons in the Middle Ages. Characterized by its matte, dark gray appearance, gunmetal has long been abandoned for use in weaponry in favor of the more durable steel, but it has retained a place in the manufacture of jewelry. When polished, it's so pretty.