In the year of retirement, a member may purchase service credit for eligibility service of up to 10 years for periods of employment for which the member: would have been entitled to purchase service credit under the Employees’ Pension System; and is not otherwise entitled to service credit under the Local Fire and Police System. To purchase service credit under this section, a member must: 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 an amount equal to the annuity reserve and pension reserve required to fund the additional allowance. A member may purchase credit for eligibility service for previous service in a position described in § 23-204(a) of this article. To purchase the service credit, the member must pay, in a single payment, the contributions, with interest, that the Board of Trustees considers appropriate.