Abstract: This mold is intended to form a cap (1) having a cylindrical skirt (3), this skirt being provided with at least one screw thread (4), a top (2) and a tamperproof ring (6) linked to the free end of the skirt by breakable linking elements. It has a movable pat or mold top (20), a stripping part or stripper ring (21) and a core (22. The stripper ring (21) has, on the side facing the top of the mold (20, on the lower edge of the skirt and in at least two separate places, at least one notch and/or at least one projection so as to create a mortise-and-tenon linkage between the skirt (3) and the stripper ring (21) during molding and demolding of the cap(1).