(1) This section applies to an existing contributor:
(a) who had, before 1 October 1972, elected under section 27 of the previous Act to have a period of service taken into account as service for pension under that Act;
(b) who had not, before that date, paid, under that section, an amount equal to the lesser of the amount of the contributions determined by the Defence Forces Retirement Benefits Board to be payable by him in respect to that period and an amount equal to 5.5% of his aggregate pay in respect of that period; and
(c) the amount of whose previous contributions is less than 5.5% of the amount of his aggregate pay in respect of his period of previous contributory qualifying service.
(2) An existing contributor to whom this section applies:
(a) shall pay an additional contribution to the Commonwealth under this section of such an amount, not exceeding the difference between the amount (if any) paid by him under section 27 of the previous Act and the amount first mentioned in paragraph (1)(b), as CSC determines as being appropriate in the circumstances; and
(b) shall not be required to make any further payments under section 27 of the previous Act in relation to the period to which the election under that section relates.