This is a charming vintage sweetheart expansion bracelet. It is sterling silver with a gold wash and the central heart is delicately etched with a flower and leaves. The links alternate between plain and embossed and it is marked in the interior Sterling Base Co-Star. I haven't been able to find out anything about this maker.
The bracelet expands and so will fit most wrists. It is about 1/2 inch wide and the heart is about 3/ inch long. It is in very good condition with some light surface wear.