Very little is known about the maker of this clock, Pietro Tommasi Campani, except that he was a member of a well-known family of clockmakers in Rome. He is known to have been working in that city about 1656-1694.
Night clocks usually have a semi-circular aperture in the dial, through which a revolving disc can be seen. The disc has two holes that reveal the hours. The hour numerals are pierced into two discs or carried on chains. The quarter hours are shown by pierced Roman numerals I-III, around the outside of the aperture and the minutes are shown as serrations around the inside of the aperture. At night the dial was illuminated by lighting an oil lamp inside the case, so that the light shone through the apertures to give the time. Campani invented his 'silent-crank' escapement with short pendulum especially for night clocks so that the clock would not make the usual tick-tock sound, which might keep the owners awake.
Petrus Thomas Campanus Inventor Rome 1683 (on the movement)