40 ILCS 5/6-118

"Prior Service Annuity" shall be credited for present employees for service rendered prior to the effective date in accordance with the provisions of the "Firemen's Annuity and Benefit Fund Act of the Illinois Municipal Code" and this Article. Each such credit shall be improved by interest until the amount of annuity to which an employee has a right is fixed. In determining such annuity, the annual salary for the entire period of the employee's service prior to the effective date shall be the salary in effect on the effective date, but not in excess of $3,000 per year.