[en] Implications of the conservation of probability without assuming CPT invariance, but allowing for the existence of a direct superweak (δC=2) interaction are studied for the charmed system D neutral-anti D neutral. We find that the values of the decay widths of the particles with definite mass lead to considerable simplifications in the phenomenological description of this neutral system. These simplifications do not occur in the K neutral-anti K neutral system. In particular, we obtain the expressions for the particle number per unit time, at time tau measured in the D neutral meson rest frame, arising from an initially pure beam of D neutral-mesons. By considering the anomalous part of the particle number expression, we find means of distinguishing between the various forms of discrete symmetry breakdown. (author)