The CP-violation mechanism proposed by Schwinger in the dyon model is discussed. It is pointed out that, once dual-charged particles are introduced, we have two kinds of smallest units of electric charge for magnetically neutral particles: one for purely electrically charged particles, the other for the magnetically neutral composites of the dyons. These two units, which, a priori, could be different, are assumed to be the charges carried by the lectron and the proton, respectively. Schwinger's mechanism can then be understood as a self-consistent condition that ensures the equality of these two units of electric charge. The analogy between this mechanism and that proposed by Bernstein, Feinberg, and Lee is discussed. The case of neutral-K decay is briefly analyzed. The magnitude of the CP-violation parameter in different processes is estimated.