of this title. finds that such fund is in excess of an amount adequate to meet future interest and principal payments on all such bonds, he may, with the approval of the Philippine Government, purchase with such excess any other bonds of the Philippines, its Provinces, cities, municipalities, and instrumentalities. For the purpose of this subsection obligations may be acquired on original issue at par, or by purchase of outstanding obligations at the market price. Any obligations acquired by the fund may, with the approval of the Philippine Government, be sold by the Secretary of the Treasury at the market price and the proceeds of such sale and the proceeds of the payment upon maturity or redemption of any obligations held in the supplementary sinking fund, as well as all moneys in any manner earned by such fund or on any obligations acquired by said fund, shall be paid into the said fund.