Alarm clocks, wall clocks, watches to be inserted on knapsacks and similar articles are provided with an interchangeable decorative member, possibly colored, which may be mounted directly on top of a fixed glass member on the clock or watch so that it is possible to repeatedly change the appearance of the alarm clock, the wall clock or the knapsack. There is provided at least one support for the decorative member which is placed on the opening of a frame of the clock or watch and which is adapted to the shape of the opening so that by the insertion of magnets or by means of pressure, the interchangeable decorative member is fixed. The decorative member may be opaque or transparent and may be made of glass, plastic, paper, a mirror or a ceramic material. The decorative member may also be mounted on a clock or watch without a support.