(A) Upon retirement from service on or after July 1, 1964, a Class One member shall receive a service retirement allowance which shall consist of:

1. (1) an employee annuity which shall be the actuarial equivalent of his accumulated contributions at the time of his retirement; and
2. (2) an employer annuity equal to the employee annuity allowable at the age of sixty-five years or at age of retirement, whichever is less, computed on the basis of contributions made prior to the age of sixty-five years; and

3. (3) if he has a prior service certificate in full force and effect, an additional employer annuity which must be equal to the employee annuity which would have been provided at age sixty-five or at age of retirement, whichever is less, by twice the contributions which he would have made during his entire period of prior service had the system been in operation and had he contributed thereunder during such entire period.

   Upon retirement from service after December 31, 2000, a Class One member shall receive a service retirement allowance computed as follows: If the member's service retirement date occurs on or after his sixty-fifth birthday, or after he has completed twenty-eight or more years of creditable service, the allowance must be equal to one and forty-five hundredths percent of his average final compensation multiplied by the number of years of his creditable service.

   If the member's service retirement date occurs before his sixty-fifth birthday and before he completes twenty-eight years of creditable service, his service retirement allowance is computed as above, but is reduced by five-twelfths of one percent thereof for each month by which his retirement date precedes the first day of the month, prorated for periods less than a month, coincident with or next following his sixty-fifth birthday.

   Notwithstanding the foregoing provisions, any Class One member who retires on or after July 1, 1976, shall receive not less than the benefit provided under the formula in effect before July 1, 1976.

(B) Upon retirement from service after December 31, 2000, a Class Two member shall receive a service retirement allowance computed as follows:

1. (1) If the member's service retirement date occurs on or after his sixty- fifth birthday or after he has completed twenty-eight or more years of creditable service, the allowance must be equal to one and eighty-two hundredths percent of his average final compensation, multiplied by the number of years of his creditable service.
2. (2) If the member's service retirement date occurs before his sixty-fifth birthday and before he completes the twenty-eight years of creditable service, his service retirement allowance is computed as in item (1) above but is reduced by five-twelfths of one percent thereof for each month, prorated for periods less than a month, by which his retirement date precedes the first day of the month coincident with or next following his sixty-fifth birthday.
3. (3) Notwithstanding the foregoing provisions, a Class Two member whose creditable service began before July 1, 1964, shall receive not less than the benefit provided by subsection (A) of this section.