According to Andrews (Amulets of Ancient Egypt, pp. 67-68), "Ba is the name given to that uniquely Egyptian combination of human head on falcon's body which represents pictorially one of the three principal spirit forms which survived death. ... The Ba perhaps embodied the characteristics or personality of a man (or woman), the individual traits which distinguished him from all other human beings. It was the Ba which revisited the world of the living, traveled across the sky in the sun god's boat and anxiously witnessed the weighing of the heart in the Underworld lest, in spite of the heart scarab, the result prevented entry in the Egyptian paradise."
Egyptian gold and cloisonné amulets are quite rare. For the type compare the example in the Brooklyn Museum of Art, no. 110 in Fazzini, Images for Eternity, Egyptian Art from Berkeley and Brooklyn.