(a) A member who has been in state service for some past period or periods not otherwise credited for retirement purposes, and for which he cannot obtain credit for retirement purposes under any other section of this chapter, may obtain credit for such period or periods of service for retirement purposes; provided he has been in state service continuously for the twelve months next preceding his written request to the Retirement Commission for such service credit, and provided he pays to the retirement fund for each month of such service a sum based on his gross yearly rate of compensation as of the date such service was rendered, and equal to one-twelfth of two per cent of any part of such compensation on which the state made contributions under a Social Security Agreement, plus one-twelfth of five per cent of any part on which the state did not make such contributions, with interest thereon at the rate of five per cent per year from the time such service was rendered or from September 1, 1939, whichever is later, to the date of payment. Such payment may be made by payroll deductions as determined by the Retirement Commission over a period not to exceed thirty-six months, with interest on such contributions at the rate of five per cent per year to be paid not later than the last day of the month following the payment of the last of such deductions; but such service credit shall not be granted unless payment of contributions and interest is completed.

(b) Notwithstanding the provisions of § 5-175b, any member of the state employees retirement system who served as a member of the General Assembly prior to July 1, 1985, may obtain credit for such service in the General Assembly not otherwise credited for retirement purposes, provided application is made to the State Employees Retirement Commission not later than December 31, 1990, and provided further such member pays to the retirement fund for each month of such service in the General Assembly a sum based on his gross yearly rate of compensation as of the date such service was rendered and equal to one-twelfth of two per cent of any part of such compensation to the amount of the Social Security maximum wage plus one-twelfth of five per cent of the excess for part B members and one-twelfth of five per cent of such compensation for part A members, with interest thereon in both cases at the rate of five per cent per year from the time such service was rendered to the date of payment. Payment shall be made in accordance with the regulations concerning prior service as prescribed by the State Employees Retirement Commission.