A coupling member to be carried by a vessel of the container forming a vessel, and a cap intended to be screwed on the coupling member. The device also includes security features including a circumferential locking stop carried by the cap, and a complementary retractable circumferential locking stop carried by the coupling member. To this end, the coupling member includes a radial arm carrying a radial front arm, wherein the radial front arm and the radial arm extend in opposite directions. The front arm bears a lug forming the complementary retractable circumferential locking stop.