What Is the Universal Precious Metal Marking System?

Gold, silver, platinum and palladium are the official "precious metals," reports the Convention on the Control and Marking of Articles of Precious Metals (Hallmarking Convention). They're mixed, or alloyed, with other metals for manufacture. Precious metal products are incised with official symbols called hallmarks that guarantee their quality and genuineness to buyers.

Required Marks

• The Hallmarking Convention established a universal precious metals' quality assurance system in 1972 to facilitate international trade. Products from member countries carry a Convention's Common Control Mark (CCM) identifying the metal and the purity or fineness of it in a particular alloy, expressed as grams of pure metal per thousand kilograms of alloy by weight. Products are also incised or "struck" with a "responsibility" mark identifying the article's maker or producer. A third mark states the fineness or amount of pure precious metal in the product. The fourth compulsory mark identifies the national assay office that tested the product, confirming its precious metal purity as stated by the responsible party.

Gold

• The gold CCM expresses the product's gold content as its fineness number in parts per thousand, flanked by a weighing balance, both inside two overlapping circles. The Hallmarking Convention does not approve any product as gold unless it is at least 325 parts gold per 1,000 parts total metal alloy by weight. Pure gold is designated 999 on the CCM, meaning that at least 999 grams of a kilogram of metal are elemental gold.

Silver

• Fineness numbers for silver are expressed as parts per thousand, by weight. The CCM for silver displays the fineness number of the stamped product between the two pans of the weighing balance or assayer's scale. The mark's outline echoes the scale in an angular pattern. CCM marks are only on products with silver fineness numbers of 800, 830, 925 and 999 or pure silver. Only silver products marked with a fineness number of 925 or higher can be marketed as sterling silver.

Platinum and Palladium

• A diamond shape surrounding the fineness number and weighing balance identifies the platinum CCM. Numbers within this precious metal's CCM are 850, 900, 950 or 999, the latter considered pure platinum. The palladium CCM outline is hexagonal. Palladium marks display only fineness numbers of 500, 950 or 999.