You have an old earring and the marking is Wells 1120 12 kgf?

The marking "Wells 1120 12 kgf" indicates that the earring is made by the Wells company and has a gold-filled (gf) composition, with 12 kgf meaning it contains 12 karat gold bonded to a base metal. Gold-filled items typically have a thicker layer of gold than gold-plated pieces, making them more durable and valuable. If you're considering its worth, the gold-filled aspect suggests it has some intrinsic value, but it may not be as valuable as solid gold jewelry.