Gold Jewelry

Gold jewelry is usually stamped with a number followed by the letter "k," which stand for karat, the unit of measurement of gold content. Pure gold is stamped 24k. This means that there are 24 out of 24 parts of gold in the jewelry. 22k means there are 22 out of 24 parts (91.6%) of gold. 18k means there are 18 out of 24 parts (75%) of gold. 14k means there are 14 out of 24 parts (58.3%) of gold. 10k means there are 10 out of 24 parts (41.6%) of gold.

Silver

Sterling jewelry is stamped 925 or .925. This means that it contains 92.5% of pure fine silver. Pure Silver is marked .999 Fine.

Platinum

Platinum marked Pt 900 contains 90% pure platinum. Jewelry marked Pt 950 has 95% pure platinum.

Other Stamps

G.F. stands for Gold Filled. G.E.P. stands for Gold Electroplate. R.G.P. stands for Rolled Gold Plate. 316L stands for High-grade Stainless Steel.

Location of Markings

Stamps and marks on jewelry are discreet so that they do not interfere or mar the design. Here are the most common places for stamps: Earrings--posts or on the basket setting. Rings--inside of the band. Pendants--on the bail. Necklaces and bracelets--on the clasp.

Source:

Original Diamonds.com: Jewelry and Gem Dictionary

Federal Trade Commission: Guides for the Jewelry, Precious Metals, and Pewter Industries

Amazon.com: Metal Stamp Information