A present employee, who has a credit on the effective date, for prior service annuity, of an amount sufficient to provide annuity as of his age on such date equal to that to which he would have had a right if employee contributions and city contributions had been made for age and service annuity during his entire service until his attainment of age 57, is entitled to a prior service annuity from the date he withdraws from service, fixed as of his age on the effective date, of such amount as can be provided by his credit for this purpose on the effective date. Any such present employee has no right to receive age and service annuity.
40 ILCS 5/6-120