This paper analyzes the observable consequences of the Bühring interior metric deformation model, a regular black hole construction that preserves the exact Schwarzschild exterior while replacing the interior singularity with a regular core. Because the exterior geometry remains unchanged, leading-order observables such as the photon sphere, shadow radius, and primary ringdown frequency coincide with the Schwarzschild prediction. Observable deviations arise only through global perturbative structure and subleading effects associated with the regular interior completion. The analysis focuses on quasinormal-mode sensitivity, late-time ringdown behaviour, and precision black hole spectroscopy as potential observational probes. The results indicate that the model does not generically produce large leading-order deviations, but instead predicts systematic perturbative corrections tied to the global boundary-value structure of the spacetime. This work is part of the Bühring Interior Metric Deformation Model series (Papers I–VII). Paper V focuses on observational implications, while subsequent papers develop the quasinormal-mode boundary-value problem and spectral structure.
Finn Bühring (Mon,) studied this question.