If you come across jewelry marked “KP”, you should know that the “P” stands for “plumb”. This marking means that the piece is guaranteed to have at least the karat value indicated.
For example, if a ring is marked 20KP, it has a gold purity of no less than 20 karats.
But why was this additional marking introduced if the karat number itself is supposed to indicate purity?
The reason has something to do with gold sellers, who are allowed to put a karat number that can differ slightly from the actual gold content of the merchandise.
In the U.S., the permitted deviation is no more than 0.5 karats. So, a ring that is actually 21.5K may be stamped with a 22K mark.
However, if the ring has the letter “P” after the karat symbol, you can assume that the gold purity is at least what the number indicates.
What If I Can’t See Any Marks?
Sometimes, there will be no marks stamped on your jewelry. In such cases, the most accurate assessment of gold purity can be made by a professional.
Usually, jewelers use nitric acid to find out the real karat of a piece. So, if you have unmarked gold and want its purity evaluated, you can always go to a jewelry store and ask to have your jewelry tested.