Okla. Stat. tit. 82 § 876
All bonds and the interest thereon issued pursuant to the provisions of this act shall be exempt from taxation, except inheritance taxes, by the State of Oklahoma or by any municipal corporation, county or other political subdivision or taxing district of the state.
Bonds issued under the provisions of this act are hereby made securities in which all public officers and public bodies, agencies and instrumentalities of the state and its political subdivisions, all banks, trust companies, trust and loan associations, investment companies, and others carrying on a banking business, and all insurance companies and insurance associations, and others carrying on an insurance business, may legally and properly invest funds including capital in their control or belonging to them. Such bonds are also approved as collateral security for the deposit of any public funds and for the investment of trust funds.
Okla. Stat. tit. 82, § 876