The calligraphy is possibly part of a Persian inscription.
The design of this tile is very close indeed to the main frieze of tiles in the shrine at Mashhad (Watson, Oliver: Persian Lustre Ware, London, 1985, pl.105). It has the same unusual white ground with design in lustre as is found in those examples, and a similarly strong arabesque upper band coupled with no appreciable lower band. The large scrolls and terminals which form the background to the main band are strongly moulded. The execution here whowever is not as fine as the Mashhad examples, the inscription not as strong, and the tile is smaller. It is probable that this was made for a less important commission, but in the same workshop as the Mashhad frieze.