Section 40 ILCS 5/20-131 - Retirement Annuities and Survivors Annuities - Guarantees(a) This amendatory Act of 1975 (P.A. 79-782) shall not be applied to deprive any person or his survivor of eligibility for an annuity or to reduce the annuity or to deprive such person of rights to which he or his survivor would have been entitled under the provisions of Article 20 which were in effect immediately prior to September 5, 1975, if he was an employee immediately prior to that date.(b) If the combined retirement annuity benefits provided under Public Act 79-782 are less than the combined retirement annuity benefits that would have been payable under the alternative formula of Section 20-122, the system under which retirement would have occurred, as provided by Section 20-122, shall increase the proportional retirement annuity by an amount equal to the difference.(c) Subsection (b) of this Section does not apply to the retirement annuity benefits payable under the self-managed plan established under Section 15-158.2 of this Code.P.A. 86-820; 91-887, eff. 7/6/2000.