Vintage 18K gold filled statement ring with large stone / crystal

Vintage 18 karat gold filled ring. Beautiful statement piece, with a large sparkly stone that is either a natural stone, or a natural crystal (and not glass as there are no inner bubbles). Size 5.75. Stamped 18 K GF and has a makers mark that I can't read. In well loved condition, with quite a bit of wear on the gold filling, as pictured. Mostly on the band and on the front edges, including prongs. Still there is a lot of gold left on the inner surfaces, and it still hurts sparkles and shines beautifully.