by the reference numeral 22 of the second cap 5 and protrudes downward so as to interact with an approximately complementarily shaped seat 23 formed in the first upper surface 11 of the first cap 4 in the illustrated embodiment the seal 21 is constituted by a plate 24 which lies on a plane that is approximately parallel and lower with respect to the plane of the second surface 22 and is associated or monolithically coupled thereto by way of a plurality of tabs generally designated by the reference numeral 25 in particular the tabs 25 are preferably equidistant and have at least one weaker region 26 such as for example a region that has a considerably reduced cross section with respect to the dimensions of the plate 24 in this manner once the first closure of the device 1 has occurred and once the second cap 5 has been lowered from the position of fig1 to the position of fig1 the interconnection by interference between third perimetric edge 27 of the plate 24 and the lateral edges of the seat 23 is achieved the plate 24 can be for example substantially circular or oval or cross shaped such as the one shown in the figures or rectangular or square or any other advantageously flat shape so long as it has third perimetric edges 27 that interact by interference in the seat 23 so as to.