An active fireman may establish a maximum of 24 months of additional service credit attributed to service in the armed forces of the United States that was served prior to employment by the city as a firefighter by applying in writing to the fund and, after substantiation of any such requested service, making contributions to the fund equal to (i) the employee contributions that would have been required had the service been rendered as a member, plus (ii) an amount determined by the fund to be equal to the employer’s normal cost of the benefits accrued for that military service, plus (iii) interest at the actuarially assumed rate provided in the Fund’s most recent annual actuarial valuation, compounded annually from the first date of membership in the fund to the date of payment on items (i) and (ii).
     This Section applies only to firemen in service on or after its effective date.