In addition to standard gold purity markings such as 10K, 14K and so on, real gold jewelry is often stamped with a three-digit code. These codes correlate to the purity of the gold within the piece. Gold marked with the numbers 825 has a purity rating of about 19K.
While it is less common to find gold marked 19K or 825 than 14K, 18K and 20K, such items do exist. The numbers may not look familiar to some jewelry buyers, but the markings indicate that the piece is real gold and of a higher purity than most jewelry. However, it's always a good idea to have jewelry professionally examined to verify that the marking is accurate.