The display unit (2) equips a portable instrument, such as a wristwatch (1) with hands (13, 14, 15) for indicating the time. The unit comprises at least one display cell (4) which comprises a transparent front substrate (41) having first transparent electrodes (45) on an interior face, a transparent rear substrate (42) having at least one transparent second electrode (46) on an interior face and a fixing frame (43) for the two substrates in order to define a closed space between the substrates. A substance (44), the optical or physical properties of which can be modified between the electrodes which are activated by a difference of potentials applied via control means, occupies the closed space between the first and second electrodes. Via the action of the control means, the display cell (4) makes it possible to display information, for example temporal information. The display unit (2) comprises also a plurality of transparent or semi-transparent stones which are supported on or in a transparent or semi-transparent support (3). The support is disposed on a front visible face of the display cell or alternatively on a rear face of the display cell in order to combine the information of the cell in a first display state with light refraction through visible rigid elements and/or light reflection on or in the visible rigid elements.