69. In the cases provided for in sections 67 and 68, if the employee again becomes a member of this plan without having obtained a refund of his contributions and, in the case of section 67, without being entitled to a refund, the years and parts of a year of service he accumulates are added to those already credited.
If, however, in the case provided for in section 68, the employee again holds pensionable employment within 180 days of the date on which he ceased to be a member of this plan, he is entitled to a refund of his contributions if he applies therefor within such 180 days.