40 ILCS 5/15-108.1: Tier 1 member.

"Tier 1 member": A participant or an annuitant of a retirement annuity under this Article, other than a participant in the self-managed plan under Section 15-158.2, who first became a participant or member before January 1, 2011 under any reciprocal retirement system or pension fund established under this Code, other than a retirement system or pension fund established under Articles 2, 3, 4, 5, 6, or 18 of this Code. "Tier 1 member" includes a person who first became a participant under this System before January 1, 2011 and who accepts a refund and is subsequently reemployed by an employer on or after January 1, 2011.