The State and all counties, cities, villages, incorporated towns and other units of local government and public bodies, and public officers of any thereof; all banks, bankers, trust companies, savings banks and institutions, building and loan associations, savings and loan associations, investment companies and other persons carrying on an insurance business; and all executors, administrators, guardians, trustees and other fiduciaries may legally invest any sinking funds, moneys or other funds belonging to them or within their control in any bonds issued pursuant to this Article, it being the purpose of this Section to authorize the investment in such bonds of all sinking, insurance, retirement, compensation, pension and trust funds, whether owned or controlled by private or public persons or officers; provided, however, that nothing contained in this Section may be construed as relieving any person from any duty of exercising reasonable care in selecting securities for investment.