Okla. Stat. tit. 36, § 36-1615: Preferred or guaranteed stock

An insurer may invest in preferred or guaranteed stocks or

shares of any solvent institution created or existing under the laws

of the United States or of any state, district or territory thereof,

if such stock and all of the prior obligations and prior preferred

stocks, if any, of such institution at the date of acquisition by

such insurer are not then in default.