Finely decorated cylinder dial. On the surface of the column are drawn the hour lines, at the top of which are the names of the months and of the zodiac signs. The movable top section has two gnomons of different length, to be used according to the time of the year of the observation. The gnomons can be folded into the instrument. There is a painted dedication to Francesco I de' Medici, suggesting a date of manufacture between 1574 and 1587, the years when the eldest son of Cosimo I assumed the title of Grand Duke of Tuscany.