To finance necessary parking facilities for the Center, the Board may issue revenue bonds to the Secretary of the Treasury payable from revenues accruing to the Board. The total face value of all bonds so issued shall not be greater than $20,400,000. Such obligations shall have maturities agreed upon by the Board and the Secretary of the Treasury but not in excess of fifty years. Such obligations may be redeemable at the option of the Board before maturity in such manner as may be stipulated in such obligations, but the obligations thus redeemed shall not be refinanced by the Board. The Secretary of the Treasury is authorized and directed to purchase any obligations of the Board to be issued under this section and for such purpose the Secretary of the Treasury is authorized to use as a public debt transaction the proceeds from the sale of any securities issued under chapter
31 of title
31 and the purposes for which securities may be issued under chapter
31 of title
31 are extended to include any purchases of the Board’s obligations under this section.