This clock belongs to the category of clocks related to the invention of the pendulum clock by Christiaan Huygens, which made the construction of accurate clocks possible. Hoevenaer was well aware of this and included a seconds dial on the dial. Before Huygens' invention clocks were so irregular that a seconds dial was not much use. This clock is one of the first clocks with a useful seconds dial. It was probably made for precise astronomical measurements, but so far no evidence has been found of this clock belonging to the Leiden Observatory. • The case of the clock is a twentieth century addition, probably because the original case was broken. The brass dial plate is covered with burned styrax. The central brass chapter ring indicates the minutes (1-60) in anti-clockwise direction. There are four subsidiary brass rings inside the central ring. In the top ring the seconds are indicated (5-60, with second division), also rotating anti-clockwise. On the left-hand ring the date (1-31) is indicated and has a day aperture within its surround. The right-hand ring indicated the moon phase whilst the hand shows the moon date (two times 1-29½). The bottom ring is an hour chapter ring (I-XII), with half hour division. The signature cartouche is an integral part of the lower pierced and engraved spandrels and is marked Anthonius Hoevenaer Fecit Leijdae • The weight-driven movement of day duration has a going train with five wheels and a striking train with four wheels. The count-wheel striking train indicates the hours on a bell, now broken. The brass pendulum with lead bob is driven by a verge escapement with a brass crown wheel. The thread-suspended pendulum has a length of approximately 25 cm, the length of a so-called half-seconds pendulum, which makes it easy to show the seconds. • For the maker see Horological Desk Diary 2014, pp. 140-41. • Literature: C.A. Grimbergen, The evolution of the Dutch clock, Zaandam, 1991, pp. 16, 17; Hans Hooijmaijers, Telling Time, Devices for time measurement in Museum Boerhaave; Leiden, 2005, p. 18; J. Zeeman, De Nederlandse Staande Klok, Assen, 1977, pp. 265-267. • Museum Boerhaave inventory number 9615.