Occasionally, a jewelry owner decides to sell a piece of his collection. The process of determining its value begins with locating the letters and numbers inconspicuously stamped on the metal.

Precious Metal Designations

Precious jewelry is most often forged from gold, silver or platinum. Pure gold is referred to as 24-karat gold, and precious gold jewelry is stamped with the letter “k” preceded by a number to indicate the amount of gold it contains. Sterling silver jewelry is often stamped with the number .925, meaning that it is 92.5 percent pure silver. If the jewelry is marked “PL,” “PLAT” or “PT,” the piece is made of platinum. The symbol for platinum on the periodical table is “Pt.”

Platinum Alloy

Platinum is a soft metal and, therefore, high-quality jewelry contains a combination of 95 percent platinum and 5 percent of a metal alloy, such as ruthenium or iridium, to give it strength. In the United States, if the platinum is less then 95 percent pure, however, the stamp must also indicate the elemental alloy such as “IRID/PL.”

White Gold and Inlays

Since white gold resembles platinum in color, a ring may actually be platinum rather than gold. The letters “PL” or “PT” also may be stamped on gold jewelry because the piece includes an inlay of platinum, a common design of engagement rings and wedding bands.