Jewelry manufacturers stamp information about the purity of precious metals. They place the stamp somewhere not to detract from the design. And the best place for the stamp is on the inside or back of the jewelry item. Or in case of earrings on the basket setting of the earrings. These stamps should adhere to strict guidelines of the Federal Trade Commission.
In the table below you can see the most common precious metal stamps. The alternative stamps or hallmarks are also listed. The table also shows the purity percentages and used alloys.
|Most Common Precious Metal Stamps|
|Metal stamp||Alternate stamp or European hallmark||Minimum percentage of pure metal||Common alloy impurities*|
|.925 Sterling Silver||925 Sterling, Sterling Silver||92.5% pure fine silver||Usually copper|
|10K||10k, 10kt, 416, 417, 10KP**||41.6% pure gold||Usually silver, copper, zinc, and nickel|
|14K||14k, 14kt, 583, 585, 14KP**||58.3% pure gold||Usually silver, copper, zinc, and nickel|
|18k||18k, 18kt, 750, 18KP**||75% pure gold||Usually silver, copper, zinc, and nickel. For white gold, palladium is also used|
|22K||22k, 22kt, 916, 917||91.6% pure gold||Usually silver and copper|
|24K||24k, 24kt, 999||100% pure gold||None|
|900 Platinum||900 Plat, Plat 900, Pt900, 900Pt||90% pure platinum||Ruthenium, rhodium, palladium, and other platinum group metals|
|950 Platinum||PLAT, PT, 950 Plat, Plat 950, Pt950, 950Pt||95% pure platinum||Ruthenium, rhodium, palladium, and other platinum group metals|
|*May vary depending on the desired color, such as white gold or rose gold|
|**”Plumb” means true or exact. Plumb indicates that the purity of the gold content is exactly what is stamped on the item. The word “Plumb” or the letter P follows the metal stamp (e.g. “14k Plumb,” “14KP”).|
- “Karat” (abbreviated as “k,” “K,” or “Kt”) refers to the relative purity of gold. Karat is 1/24th, hence 24 Karat gold is pure gold. But “Carat,” is a metric unit of weight and is equal to 200 mg.