The Commonwealth and all public officers, municipal corporations, political subdivisions (other than housing authorities), and public bodies, all banks, bankers, trust companies, savings banks and institutions, building and loan associations, savings and loan associations, investment companies and other persons carrying on a banking business, all insurance companies, except domestic life insurance companies may legally invest any sinking funds, moneys or other funds belonging to them or within their control in any bonds or other obligations issued by a housing authority pursuant to the Housing Authorities Law, or issued by any public housing authority or agency in the United States, when such bonds or other obligations are secured by a pledge of annual contributions to be paid by the United States government or any agency thereof, and such bonds and other obligations shall be authorized security for all public deposits and shall be fully negotiable in this Commonwealth; it being the purpose of this act to authorize any persons, firms, corporations, associations, political subdivisions, bodies and officers, public or private, to use any funds owned or controlled by them, including (but not limited to) sinking, insurance, investment, retirement, compensation, pension funds, and funds held on deposit, for the purchase of any such bonds or other obligations and that any such bonds or other obligations shall be authorized security for all public deposits and shall be fully negotiable in this Commonwealth; provided, however, that nothing contained in this section with regard to legal investments shall be construed as relieving any person, firm or corporation from any duty of exercising reasonable care in selecting securities.