40 ILCS 5/9-150.1

The provisions of parts (1) (b) and (c) of Section 9-150, of this Article 9, increasing the maximum widow's annuity from $300 to $400 a month, shall be effective July 1, 1971, and apply in the case of every qualifying widow whose husband dies while in service on or after July 1, 1971 or withdraws and enters on annuity on or after July 1, 1971.