Antique 1 20th 12K GF Circle Pin with Rose and Topaz Rhinestones in Octagon and Chaton Cuts Marked DO?

Stunning 1/20th 12K Gold Filled circle pin in yellow and rose gold with a rose across the circle. At the bottom of the circle is an octagon cut topaz rhinestone and on the side a chaton cut stone. It is in very good to excellent condition with what looks like a D&O mark on the back with the 1/20th 12K GF mark.