This nocturnal consists of three overlapping disks of different diameters: the largest shows the zodiacal calendar; the middle one carries the hours and the index; the smallest—a toothed disk—has a long index arm and the inscription "Horologium nocturnum." On the back are engraved a sundial and a shadow square. The instrument closely resembles items inv. 2503 and inv. 3811, and was probably made by Girolamo della Volpaia. Provenance: Vincenzo Viviani bequest.