The male can be identified by the slightly concave shape to its plastron. At one end is a black granite fountain with a double concave shape. Its mouth was nearly turned upwards, thereby giving the flat head a concave shape. Beads are a convex shape relative to the cylinder, and coves are a concave shape. The underlying calyces lose their normal concave shape and show clubbing. The main advantage of wok beyond its constructed material is its curved concave shape. The gorget forms a concave shape and, when engraved, the interior is polished and decorated.