All bonds issued under this chapter are legal and authorized investments for all banks, savings banks, trust companies, building and loan associations, savings and loan associations, and insurance companies of all kinds and types, and for the interest and sinking funds and other public funds of any issuer. The bonds are also eligible and lawful security for all deposits of public funds of the State of Texas and of any issuer, to the extent of the value of the bonds, when accompanied by any unmatured interest coupons appurtenant to them.