Conjugation symmetry in linear electromagnetism in extension of materials with negative real permittivity and permeability scalars

If all space is occupied by a linear bianisotropic material - whether homogeneous or not - then the concurrent replacements of the permittivity and the impermeability tensors by the negatives of their respective complex conjugates and of the magneto-electric tensors by their respective complex conjugates (in the Boys-Post representation) imply the conjugation of both E and H, in the absence of externally impressed sources. This conjugation symmetry in linear electromagnetism has observable consequences when the linear bianisotropic material occupies a bounded region.