C. 1980 Vintage Red Carnelian Intaglio Ring in 18kt White Gold. Size 4

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.

WHITE GOLD: Gold is a precious metal which is naturally quite soft. To give it a white color and increase its strength, gold is alloyed with white metals, such as silver and/or palladium, and often plated with rhodium. The purity of the metal is indicated by a unit called a "karat," with 24kt having the highest percentage of natural gold.

CARNELIAN: A brownish-red mineral, carnelian has been used for centuries to make engraved gems and signet rings, intaglios and especially seal rings, because hot wax does not adhere to it. Its name comes from the Latin word for cherry, since the lush red color of the carnelian so resembles the vivid red fruit.

OCTAGON: A symmetrical shape with eight equal sides.

INTAGLIO: A carving that is engraved below the gemstone's surface to create a particular design.