Section 18. Bonds and notes issued under this chapter are hereby made securities in which all public officers and public bodies of the commonwealth and its political subdivisions, all insurance companies, trust companies in their commercial departments, investment companies, executors, administrators, trustees and other fiduciaries may properly and legally invest funds, including capital in their control or belonging to them, and such bonds and notes are hereby made obligations which may properly and legally be made eligible for the investment of savings deposits and the income therefrom in the manner provided by paragraph two of section fifty of chapter one hundred sixty-eight. Such bonds and notes are hereby made securities which may properly and legally be deposited with and received by any state or municipal officer or any agency or political subdivision of the commonwealth for any purpose for which the deposit of bonds or obligations of the commonwealth is now or may hereafter be authorized by law.