Method of producing an administering device for infusing or injecting a product, whereby in order to mold a housing shell serving as a case for components of the administering device in a multi-component injection molding process at least one pre-molded, transparent insert part made from a first plastic material is inserted in an injection mold molded to a shape matching the shape of the housing shell, a dimensionally stable, curable second plastic material is injected into the injection mold around the insert part to render it watertight and an opening left free in the second plastic material is closed to render it watertight by injecting on an elastomeric third plastic material.