second assembly element 13 this articulation rod 14 passes through the opening 9 d in the linking member 9 thus securing this linking member and the two assembly elements together this articulation rod 14 also passes freely through a member 15 for actuating the opening of the clasp i e for separating the attaching members 4 and 10 which is articulated about the second articulation pin of the linking member 9 consisting of the axis of the opening 9 d this actuating member 15 includes two opening levers 16 17 each comprising a semicylindrical element 16 a and 17 a respectively each traversed by an opening of which only the opening 17 b can be seen in fig1 for the passage of the articulation rod 14 the transverse distance separating the respective outer lateral faces of the two semicylindrical elements 16 a 17 a is very slightly shorter than the width of the recess 2 a of the branch 2 of the clasp in order to allow the pivoting of these elements 16 a 17 a about the articulation rod 14 these levers 16 17 are formed from two bearing elements 16 c and 17 c respectively secured to the respective semicylindrical elements 16 a 17 a these bearing elements 16 c 17 c extend outside the respective outer lateral faces of the semicylindrical elements 16 a 17 a such that they.