An insurer may invest in tangible personal property, or interests therein evidenced by trust certificates or other instruments, and a right to receive rental, charter hire, purchase or other payments for the use or purchase of such personal property adequate to return the investment and payable or guaranteed by 1 or more governmental units or instrumentalities whose obligations would qualify for investment under § 1306 of this title (public obligations) or 1 or more institutions whose obligations would qualify for investment under § 1308(a) or under § 1308(c)(2) or (4) of this title (corporate obligations). No insurer shall make an investment pursuant to this section if the aggregate amount so invested will exceed 5% of its assets or if the aggregate amount so invested as to which such rental, charter hire, purchase or other payments are payable or guaranteed by any 1 governmental unit or instrumentality other than the United States or Canada or any 1 institution will exceed 1% of such sets.