 < 10-20 MeV, a Delbrück experiment measures a number of competing coherent processes including also Rayleigh scattering from electrons, Thomson scattering from the point nucleus and nuclear excitation via the Giant Dipole Resonance.Apart from the Thomson scattering which is well known, the other two (namely Rayleigh and GDR) have considerable uncertainties.The interference of these effects with Delbrück is by no means "minor" (again "at classical nuclear physics energies").