40 ILCS 5/8-184

Each male employee who on June 30, 1935 was an employee of the board, shall be credited with 1 3/4% of his annual salary during his service between the day before the effective date and July 1, 1935, or the date he attained age 65 prior to July 1, 1935, for the term of service, with interest thereon at the effective rate to July 1, 1935, or the date he attained age 65, upon the assumption that 1/12 of such 1 3/4% of such annual salary was due on the last day of each month of service.