Okla. Stat. tit. 70 § 2208
Any bank, trust, or insurance company organized under the laws of Oklahoma may invest its capital, surplus, and reserves in bonds issued under the provisions of this act. The officers having charge of any sinking fund or any other fund of the state or any department, agency, or institution thereof, including the various funds established by Chapter 27 of Title 70 (House Bill No. 244 of the Session Laws of 1945), or any county, city, town, township, or school district in the state, may invest such funds in bonds issued under the provisions of this act at the reasonable market value thereof. 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. 70, § 2208