Scientific, electrical, optical, monitoring and measuring apparatus and instruments, namely devices for measuring and/or controlling the thickness of material and/or coatings by means of magnetic inductive methods; instruments for measuring the thickness of layers of non-ferrous metal coatings, paint, enamel or plastic coatings on steel or iron; probes for measuring layers of non-ferrous metal coatings, paint, enamel or plastic coatings on steel or iron as materials, layers and/or coatings; d...