we would love to see the front of this brooch! The clasp on reverse of pin can be repaired by a reputable jeweler experienced in handling Antique Jewelry. If you don't know one, please use Contact Form, for further assistance. Please tick the Jewelry Repair box.
STAR is a trade name used by A. WITTNAUER (New York, USA) - ca 1860s - 1940s
I am not sure if this is the one, but a good place to start hunting.