Comparison of radiative and buoyancy ages as a function of the magnetic field for the dying source WNB 1734+6407 in A2276. The radiative age (green line and shaded region) is derived from the spectral break measured by Murgia et al. (2011). The horizontal blue dashed line and shaded region is the buoyancy age for the south lobe. The two ages match at 65 Myr for B ≃ 12   μG. This value for the source’s magnetic field (dotted line) fits within the equipartition range for k = 1 pictured by the vertical shaded region in red.