The mark 825 on jewelry indicates that the piece is made from real gold and has a gold purity rating of approximately 19 karats. Jewelers use three-digit marks to represent the gold purity level since standard markings, appearing stamped as 14K for example, can be off by a half-karat.
Three-digit gold marks indicate the purity percentage with greater accuracy than standard ratings. For example, 825 represents a purity rating of 82.5 percent, meaning that the piece contains more than 82 percent gold. When compared to the standard marks, three-digit marking simplifies the equation for finding the purity percentage of a piece of jewelry.