I picked up this brooch at a rummage sale around 40 years ago and I've never tried to find out more about it (the stone - glass, most likely - has always been scuffed as you see in the photo). The maker's mark is cut off, but the lettering in STERLING looks similar to some Mexican pieces I have. Does anyone recognize what can be seen of the name above it? Borna? Donna? Dana? Your guess is probably better than mine!