Any active and contributing member of a city retirement system that participates in the Employees’ Retirement System under Section 36-27-6 who rendered prior service to a non-participating employer funded by a city and a county which was eligible for participation in the Employees’ Retirement System under Section 36-27-6, may purchase up to eight years of credit in the Employees’ Retirement System for the prior service if the member pays to the Secretary-Treasurer of the Employees’ Retirement System prior to the date of his or her retirement a sum equal to the full actuarial determined cost for each year of service purchased as determined by the actuary for the system. The local governmental entity which currently employs the member shall furnish the Employees’ Retirement System with documentation of the prior service being claimed by the member as requested by the retirement system. Notwithstanding the foregoing language, no member of the Employees’ Retirement System shall receive credit for any service that the member is already credited with in the system or in any other retirement plan, with the exception of the federal Social Security program.