The throne bears the ring, inserted into a rotating pivot. The limb of the instrument is divided into 360? marked off in groups of 5?. The rete bears 23 stars indicated by silver studs. The signs of the zodiac are named in Latin on the zodiac circle. Numbers and words are in gothic characters.
The back of the astrolabe bears a division from 90? to 0? and 0? to 90?, repeated twice. This is followed by the signs of the zodiac, the months (both in Latin) and a circumference with divisions from 1 to 28 beginning with the diameter. Under the diameter, the half shadow square is engraved, accompanied by the inscriptions 'VMBRA VERSA', 'VMBRA DIRECTA', repeated twice. The pointer is provided with sights at its end. In the centre of the same pointer, close to the pivot, small motifs using leaves have been engraved.
Inside the mater, which has no markings, are three plates, two of which are calibrated for the latitudes 41 and 42?, 43 and 44? (the latter in non-gothic characters). One face of the third plate is marked with the projection of the heavens, incomplete and without a latitude. Several lines are traced on the other face.
A crack runs across the instrument, reaching as far as the limb.
See M. Miniati, Museo di Storia della scienza: Catalago (Florence, 1991), p. 8.