A stopper device includes a base adapted to be fastened to a neck of a container, and a cap movable relative to the base between closed and open positions. A strand in an unaltered configuration extends along a periphery of the cap. First and second longitudinal ends of the strand are connected to the cap frangibly and non-frangibly, respectively. A hook protrudes toward an outside of the base, and when the strand is in the unaltered configuration, the hook retains a running portion of the strand, blocking movement of the cap from the closed to the open position. The first end of the strand includes a tab for detaching the first end by breaking the frangible connection and moving the running portion toward an outside of the cap until the cap may freely move from the closed to the open position without the running portion being retained by the hook.