The invention concerns the polymers obtained by the use of sulphur compounds in a process for controlled radical polymerization in water of acrylic acid andor acrylic acid with hydrosoluble monomers. The case band has a circular upwardly directed protrusion to which a transparent dial cover is mounted, a surrounding wall portion forming between itself and the upwardly directed protrusion an arrangement groove extending along this protrusion, and open portions for bezel operation. The stiff support layer cooperates with one or more water impermeable layers that reduce or prevent the flow-through of water or other liquids inadvertently spilled over the keyboard.