This is the earliest dated astrolabe in the NMM collection, and one of eight known examples from Ayyubid Syria and Egypt. It is a fine, professionally-executed instrument whose design is typical of the earliest known Islamic astrolabes. Two other pieces by this maker are extant: one in the Salar Jung Museum, Hyderabad (IC no. 4160), the other in the Raza Library, Rampur (IC no. 3765). Both are dated slightly earlier than this instrument.

The throne, cast with the rim and mater in one piece, comprises three plain lobes with wavy extensions on each side. The shackle and rim appear to be original. The maker's signature is engraved in unpointed Kufic on the back of the throne: 'Made by al-Sarraj the muezzin in Damascus in the year 628'. On the mater is a geographical gazetteer of 38 localities, displaying longitude, latitude and qibla. It is engraved by a different hand to the rest of the instrument and is a later addition, probably from the later half of the 13th century. The rete is of simple design, similar to AST0546, and has 25 dagger-shaped star pointers. There are four original plates and one replacement, possibly by the same person who engraved the gazetteer. They cover latitudes from 21°-42°. On the back of the instrument are two sine quadrants in the upper half and a double shadow square underneath.