C. 1980 Vintage Blue Agate Cameo Pin/Pendant in 18kt Yellow Gold

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.

YELLOW GOLD: Gold is a precious metal with a natural yellow color. It is quite soft and often alloyed with other metals to increase its strength. The purity of the metal is indicated by a unit called a "karat," with 24kt having the highest percentage of natural gold.

PUSH-PULL: Seen mostly on estate pins, a push-pull safety is a tube-like mechanism that slides over the end of the pin to secure it.

HINGED: A bale with a hinge. The hinge allows the pendant to be placed on and taken off a chain easily and without sliding. Ideal for putting pendants on chains that have large clasps.

AGATE: a variety of chalcedony, agate covers a rainbow spectrum of colors from black and gray to brown, pink, blue and yellow. Agate can be textured and exhibit a variegated layered stripe effect, which makes it a wonderful stone for carved cameos and beaded necklaces and bracelets.

CAMEO: A low relief carving where the carving is above the background layer. Usually carved in shell or stone to portray the profile of a woman.