The thistle is made from a nicely faceted stone that we call a Cairngorm - similar to a citrine or light topaz - second picture shows the color best. All prongs holding the stone are present. There is nice etched engraving around the pin with thistles. It measures 1 inch across and is marked STERLING SILVER on the back with W.Bs and a Z. It has a ring clasp so is after 1921.