A conductive seal that is formed on a first sealing surface by extruding an elastically curing material intermixed with conductive particles is in addition intermixed with magnetic particles. After applying the material to the first sealing surface, its cross section profile is expanded to an adjustable level towards a second sealing surface and/or sealing rims are molded to it by a magnetic force from an electromagnetic plate. The magnetic and conductive particles are preferably concentrated in the marginal sections, particularly due to magnetic forces that act on the sealing roving in the extrusion process.