So beautiful, this is a lace pin, also known as a Fichu. These small brooches had the specific task of pinning closed the lace Fichu (a type of neck scarf). Fichus were fashionable from the early 18th century well into the 19th century.
The surface is a lovely sky blue enamel, centered with an elongated pearl set star, the enameled center is framed with a row of tiny pearls. The saw tooth edge is one of those wonderful details that lets you see some original saw and tool marks from its original construction. This piece is all original and in very good condition for its age, it dates to the Early 1800s.
Usually quite decorative since they were so prominently displayed, these pins are always small, this one measures .94" by .71" wide. The pin extends beyond the body of the brooch and when poked back thru the fabric this extra length acts as a safety. There is an original engraving on the back it says "LD" in lovely hand engraved script.