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.
S.C. Code § 9-1-1550