 In the Göttingen experiment Delbrück scattering was observed as the dominant contribution to the coherent-elastic scattering process, in addition to minor contributions stemming from atomic Rayleigh scattering and nuclear Rayleigh scattering.This experiment was the first where exact predictions based on Feynman diagrams, were confirmed with high precision and, therefore, has to be considered as the first definite observation of Delbrück scattering.For a comprehensive description of the present status of Delbrück scattering 
see.