Initial donor and gainer masses (top) required to match the present masses and orbital period of V643 Ori if total mass and angular momentum are perfectly conserved, as a function of the chosen initial period. The amount of mass transferred is also indicated. Bottom panel: size (radius) of the limiting Roche lobe of the donor (and gainer) at the chosen initial orbital period. Mass transfer by Roche lobe overflow begins when the donor reaches this size during its normal evolution.