This is a replica of the ivory and gold goddess inside the Parthenon. Visitors to the great temple encouraged a trade in reproductions of the cult figure. Despite its rough unfinished appearance and small size, this particular one reproduces scenes on the shield and the base that are not on the larger Varvakeion replica. We know from the writings of Pliny and Plutarch that these were scenes of battles with Amazons and the birth of Pandora respectively.
Thanks to copies like this one we have a rough idea of what the lost original Athena Parthenos by Pheidias looked like
Athens National Museum 128
Purchased in 1884 from Martinelli of Athens
Lippold: Griechische Plastik, 146 (n.6)
Richter: Sculpture & Sculptors of the Greeks (1950), 218, fig.601
Walston: Catalogue of Casts in the Museum of Classical Archaeology (1889), 55, no.251
Lawrence: Classical Sculpture (1928), 196 & n.2
Hurwit: The Athenian Acropolis (1999), 25
Found near the Pnyx, a hill in Athens not far from the Acropolis. Later in the collection of Count Lenormant