Hi Sue, what a superb example of late Victorian Jewelry. there was a rage for "high neck dressing" during the 1890's.
A neckband of velvet or ribbon about two and a half inches was in vogue. In order to increase the height a pleating of Silk o Ribbon growing narrower in the front and flaring at the back was sewn inside the band.
This pin, I imagine, would serve as a useful adornment in conjunction with High Neck Dressing. As always, royalty influenced fashion and jewelry. And Alexandra, Prince Edward's wife, influenced fashion even before she became queen. High necklines complimented her long, graceful neck and she wore high necklines frequently. The Sunburst star and moon was popular motif in the late Victorian era.
About the initial marks on the pin, it could be just the angle of the camera, but the initials look, to me like SS?
