What does it mean when a ring is stamped 10K FG?
I found the answer to what the "325" means... It is valuable
according to this information:
What does the stamp 325 mean on jewelry?
Answer
That indicates the purity of the metal. Coins and gold bars are
usually 999,9 out of 1000. In this case, the item contains 325 out
of 1000 parts of pure (gold). In jewelry, the rest is usually
filled with fine gold and gold mixed with other fine metals.
Sterling silver has a purity of 975 out of 1000.