Any constitutional officer who has been a member of the South Carolina Retirement System and who has at least ten years of creditable service either as a constitutional officer or as a member of the General Assembly, or a combination of both under the System and who has separated prior to May 28, 1965 may elect to come under the provisions hereof; provided, he makes such election on or before December 31, 1965, and has not withdrawn his contributions from the System. Such constitutional officer shall make yearly contributions to the System in an amount equivalent to contributions payable by active members of the General Assembly.
S.C. Code § 9-1-540