Vintage Irish Silver Necklace

Heavyweight pendant on a long chain. Large semi-translucent brown stone dangles in the center of the pendant. The stone looks like brown moonstone, but I can't be sure. The surrounding silver circular piece is hallmarked on the back. My mother-in-law bought this necklace when they lived in Ireland, which would be about 50 years ago. Includes 30" long chain (15" drop). Pendant measures about 2" x 2". A very striking piece with a chunky sweater.