The board shall ascertain the contributions of each employee who on June 30, 1923, was a contributor to any municipal pension fund then in operation in the city under the Public School Employee's Pension Act of 1903, and which were applied to such fund between the day before the effective date and July 1, 1923. Each such employee shall be credited with the total employee contributions with interest thereon at the effective rate from the last day of each month in which any such amount has been contributed to July 1, 1923.
40 ILCS 5/8-175