C. 1980 Vintage House of Gubelin 1.60 ct. t.w. Diamond Swirl Collar Necklace in 18kt Two-Tone Gold. 17.5"

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.

TWO-TONE GOLD: Gold is a precious metal which is often alloyed with other metals to increase strength and create different colors. A two-tone gold piece includes two 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.

SAFETY CHAIN: A chain that is attached to both sides of the opening for a necklace or bracelet. It provides an extra measure of security in case the main clasp fails.

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.

Color Grade G-H: Near-colorless

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

CLARITY SI1: Slightly Included. Inclusions are noticeable under 10x magnification.