Read the stamp
What does 10K GF mean on jewelry
10K GF describes a mechanically bonded layer of 10-karat gold alloy over another metal. It does not state that the entire piece contains 41.7% gold.
10K belongs to the surface layer
10K is ten parts gold out of twenty-four, approximately 41.7% gold in the layer. A fraction such as 1/20 states how much of the object’s metal weight that alloy layer represents. It does not state that the entire piece contains 41.7% gold.
What to check next
Compare GF and RGP, which describe mechanically applied layers, with GP and HGE, which describe plating. Look at the entire coating stamp before interpreting a karat number. At worn edges the base metal may be visible; a maker signature beside the construction mark identifies the company.