This splendid altar clock, repeats the form of “nocturnal clocks”, which enabled the time to be read at night, but it lacks any system of internal lighting. Also typical of nocturnal clocks is the theme of the allegorical scene decorating the dial, attributed to the painter Giovan Battista Gaulli, called Baciccio (Genoa, 1639-1709). Here the Time, winged and robed in red, discovers the naked figure of Truth, who holds in her right hand the Sun and expels Falsehood. On the semicircle of the hours appear two inscriptions which allude to the transience of time.