The numbers and letters on jewelry indicate the metal and karat weight of the jewelry, and sometimes the stone. The exceptions are the low numbers, 6 through 10, because those are ring size marks.
As new alloys are added to the jewelry-making industry, the list of marks inside jewelry grows. Common marks, however, include numbers beside a letter "k," such as 14k for 14-karat gold, and 24k for 24-karat gold. In less expensive jewelry, SS is a common marking, indicating the item is made of stainless steel. Sometimes, stones are also noted in the markings, with SOL indicating a diamond solitaire, and CW indicating carat weight of the stones.