This work is a continuation of the first part with the same name, where (for solving direct and inverse magnetic thickness gauging problems) formulas are derived for an arbitrary external field for the calculation of resultant magnetic fields for two-layer magnets that contain double integrals over the entire coordinate plane from functions that are determined by the particular type of external field. The sensitivity of the resulting field to the value of the gap between the product and measurement point of this field was analyzed. The correctness (under certain conditions) of the solution to the inverse thickness gauging problem (the unambiguous determination of the thickness of the upper layer of an inhomogeneous magnet from the measured resulting field) is grounded.