This elegant astrolabe relates to a group of six Western Islamic astrolabes made in Toledo around 1060. It is most similar to an astrolabe dated 1068 by Ibrahim ibn Sa'id al-Sahli in the Museum of the History of Science, Oxford (inventory no. 55.331) and may even have been based on this instrument. Its origin is puzzling: two plates have engraved names of French cities which imply that it might have been made in France, but the design of the throne suggests that it may have come from 11th-13th century Islamic Spain. This instrument, given like so many others by Sir James Caird, the Museum's single greatest benefactor, was christened 'The Caird Astrolabe' by a unanimous vote of the Trustees on 4 July 1938.

The throne comprises a centrally positioned bracket flanked by four lion-shaped figures. It is cast in one piece with the limb and the mater. There are seven plates with stereographic projections on all 14 sides corresponding to latitudes: 12º/24º, 39º/40º, 45º/46º, 33º/36º, 30º/32º, 43º/44º and 47º/48º. On the rete, the star pointers are needle shaped and spring from fretted bases. The strap outside the ecliptic is supported by three elaborate constructions in the Arabic style. On the back of the instrument is a combined scale for degrees and the zodiac and a scale for the civil calendar. The rest of the back consists of a shadow square and a 28 year almanac. Near the centre are two crudely engraved letters: 'B M'; perhaps the initials of a former owner, but certainly not engraved by the hand that executed the rest of the instrument.