Rare-earth permanent magnets are coated in order to avoid corrosion. When considering the rated geometrical properties of a sample, the coating thickness has to be known precisely as it wrongly enlarges the magnetically active volume which in turn affects the accuracy of the measured magnetic properties. In this work, the sensitivity of hard magnetic material property measurements regarding the consideration of different coating thicknesses is evaluated. Moreover, the impact of eddy current effects on the magnetic properties is studied when measuring in an open circuit. Additionally, an outlook for a measurement-based determination of the electric conductivity of permanent magnet samples is given.