Part for attaching an outer last coil of a balance spring of a horological movement

A part arranged to attach a balance spring of a horological movement, said balance spring, wound in coils in a plane, being delimited by first and second faces which extend at a distance from one another, said attachment part comprising:

• elastically deformable clamping devices which are arranged to be brought into contact with the balance spring in order to exert a resilient clamping force on said balance spring so as to guarantee immobilisation thereof, said resilient clamping force being exerted along at least a first line of contact (A;
• B) on the first face of the balance spring and along a contact surface(S) on the second face, the first face and the second face being parallel to the plane of the coils,
• wherein the clamping device takes the form of separate first and second clamping devices which face one another, and
• wherein the first and second clamping devices take the form of two elastically deformable arms, the two arms being arranged such that free ends of the two arms face one another and are both brought into contact with the first face of the balance spring, the first face of the balance spring being located on a free end of an outermost coil of the coils of the balance spring in order to exert a resilient clamping force (F1) on said free end in a direction (Z) perpendicular to a plane (X, Y) wherein the balance spring extends.