A cover operates with a bistable snap-fit mechanism for positioning on a closable opening of a container or on another element to be closed by the cover. The cover and/or a container wall region has fitted thereon a tamper-evident sealing element to be removed when opening the container for the first time, which, prior to being removed, blocks deformation of the front wall necessary for changeover between the two bistable states and/or prevents an expansion portion necessary for the snap-fit mechanism, from bringing about alteration to the outer circumference of the cover necessary for deformation of the front wall of the cover between the two bistable states. As an alternative, or in addition, it is also possible for a handle member, necessary for pulling off the cover, to be configured such that it can only be used once the tamper-evident sealing has been successfully removed.