Abstract: Provided with a base body (1b), with its corresponding cover (1a) and the ridge (1c) which connects them, said base body (1b) contains inside it a lug (2) articulated to same at (2b) and connected at its other end (7), also by articulation, to the ridge (1c) of the case or to the cover (1a) so that said lug (3) is displaced towards the bottom (1b) and is separated from same, during the case closing and opening operations. The lug (2) incorporates the seating and fixing means for the disc, specifically a series of flexible pins (5) capped with retaining teeth (5a), which, when the lug (2) is raised, may be connected in the orifice of the disc, and which, when the said lug drops during the case closing operation, are projected outwards by a spindle (6) integral with the bottom (1b) of the case, causing locking of the disc.