  We calculate the magnetic-field dependent nonlinear conductance and noise in
a macroscopic inhomogeneous system. If the system does not possess a specific
symmetry, the magnetic field induces a nonzero third cumulant of the current
even at equilibrium. This cumulant is related to the first and second voltage
derivatives of the spectral density and average current in the same way as for
mesoscopic quantum-coherent systems. The system provides a robust test of a
non-equilibrium fluctuation relation.
