I would date this beautiful old pin to about 1910 - 1920. It has a classic style that will compliment a variety of outfits. It's pearls show signs of wear and a few have been replaced with faux but they could easily be changed if the bother you.
The back is hallmarked Sterling with no makers mark. It measures 2-3/8'' x 1-1/2'' to the bottom of the dangle. The paste stones are gorgeous, all in place and appear to be original. Aside from the pearls this is a wonderful old piece.