Any member of the Employees’ Retirement System of Alabama who was prohibited from participating in the Employees’ Retirement System because such member was age 61 or older at the time of his employment may purchase credit for any such service including service rendered subsequent to October 1, 1988, for which the member would have been eligible for coverage except for his age, provided that such member shall pay to the Secretary-Treasurer of the Employees’ Retirement System within one year after October 1, 1989, a sum equal to the total contributions which he would have made as a member during the period of such employment plus eight percent interest on such total contributions compounded annually from the date of such service.