A member of the Employees’ Pension System who as of July 1, 2001, has been employed by the State for at least 40 years on a full-time or part-time basis may purchase credit for eligibility service of up to 10 years for which the member is not otherwise entitled to service credit. This section does not apply to: an employee of a participating governmental unit or a former participating governmental unit that has withdrawn; or any period of employment during which an individual participated in the optional retirement program. A member who purchases service credit under this section shall: complete a claim for the service credit and file it with the Board of Trustees on the form that the Board of Trustees provides; and pay to the Board of Trustees the member contributions the member would have made for the period of employment for which service credit is being purchased plus regular interest to the date of payment. A member may pay the amount required by paragraph (1)(ii) of this subsection on an installment basis by contributing at least 2% of earnable compensation per year with the appropriate final adjustments being made in the year the member retires. A member may pay for service credit purchased under this section at any time before retirement. A member who purchases service credit under this section may not purchase more than a total of 10 years of service credit for periods of employment with the State. For service credit purchased under this section, a year or a part of a year of employment equals 1 year of service credit.