Vintage Sterling Earrings with Opal and Gemstone Style Stones

Sterling silver dangle earrings - these are signed, and the sterling is marked. They were sold to my mother in the 90s new as opal and genuine gemstone earrings - and I’ve seen the same vintage earrings being sold elsewhere online as genuine opal and gemstone - but looking more closely at it, I think the stone may be glass. If the stone is glass, the opal may be simulated too - so I’m pricing these lower because I’m not sure myself what the components are. Marked 925 and the makers mark is MF with a copyright symbol.