Astrolabe complete with rete and alidade, comprising eight tympanums for different latitudes. On the back, there is a zodiac belt, a calendar, the shadow square, the horary quadrant, and, on the alidade, markings for the ante- and post-meridian hours. Its structural characteristics suggest that it was made by Gualterus Arsenius in c. 1570. Provenance: Medici collections.