This rather strange-looking object is in fact a decorative wall plaque. Such plaques were popular in royal palaces and similar examples are known later from Assyria. This plaque has a cuneiform inscription which reads: 'palace of Untash-Napirisha'.
Untash-Napirisha was the king of Elam, the name given to the south-western part of Iran in antiquity. Under his reign Elamite control stretched from the Persian Gulf to Anshan in Fars province, and included the region of Susa. The site of Choga Zanbil, forty kilometres south-east of Susa, was called in antiquity 'Al Untash-Napirisha (city of Untash-Napirisha) after the king. He founded the city, which may have been a religious or ceremonial centre, as it includes a magnificent ziggurat, as well as other shrines and temples.
J. Curtis, Ancient Persia (London, The British Museum Press, 1990)