Closing/opening system for a timepiece case

A closing/opening system for a case of a timepiece including first and second parts, the system comprising:

• a device for producing a mechanical connection between the first and second parts;
• a device for creating a friction torque between the first and second parts, the device for creating a friction torque including tightening faces configured to cooperate with one another when closing/opening the case and which are defined in said first and second parts;
• a tightening element in one of the two tightening faces, said tightening element being configured to generate a constant friction torque during a course of travel of one of the two parts relative to the other when closing/opening the case of the timepiece,
• wherein the tightening face in which the tightening element is comprised includes a recess formed by two parallel walls separated by a bottom wall that is perpendicular to the parallel walls, the recess including an opening at a top of the recess and the tightening element is in contact with the bottom wall of the recess and projects outward from the opening at the top of the recess.