C. 1985 Vintage .15 Carat Diamond Knot Ring in 18kt Tri-Colored Gold. Size 6

18KT: Karat (abbreviated kt or K) is a unit that indicates the purity of gold in the metal. 18kt is 75% gold. In Europe, 18K yellow gold is most favored and used in jewelry.

TRI-COLORED GOLD: Gold is a precious metal which is often alloyed with other metals to increase strength and create different colors. Sometimes called "tri-tone," a tri-colored gold piece includes three colors of gold: yellow, rose, white, or gunmetal-finished gold. The purity of the metal is indicated by a unit called a "karat," with 24kt having the highest percentage of natural gold.

Diamond: The hardest and most brilliant of all gemstones, a diamond can make the heart race with its pure and fiery spark. An ancient symbol of love, a diamond is the preferred gemstone for tokens of affection, such as rings, earrings, necklaces and bracelets. Diamond is the birthstone for April.

BRILLIANT: A gemstone cut to enhance brilliance without sacrificing much carat weight. Typically has 58 facets.

Clarity VS2: Very slightly included. Inclusions are observed with effort under 10x magnification, but can be characterized as minor.