Section 40 ILCS 5/16-134 - Additional retirement annuity(a) An annuitant receiving a retirement annuity on June 30, 1947 who has at least 25 years of creditable service shall upon attaining age 60 or thereafter have his or her annual retirement annuity increased to $700 for an annuitant who is age 60 and by an additional $30 for each year of age attained above age 60, but not exceeding a total annual retirement annuity of $1,000.(b) In order to be entitled to such increase in retirement annuity, the annuitant is required to make an additional contribution of $300 together with interest at the rate of 3% per annum from June 30, 1947 on any part of such $300 not paid on such date.(c) The additional retirement annuity provided under this Section shall begin to accrue on the first of the month following receipt of the required contributions from the annuitant.