Okla. Stat. tit. 36, § 1512

A. Securities, other than those referred to in Section 1511 of this article, held by an insurer shall be valued, in the discretion of the Insurance Commissioner, at their market value, or at true book value, all consistent with any current method for the valuation of any such security formulated or approved by the National Association of insurance Commissioners. B. Preferred or guaranteed stocks or shares while paying full dividends may be carried at a fixed value in lieu of market value, at the discretion of the Insurance Commissioner and in accordance with such method of computation as he may approve. Laws 1957, p. 285, § 1512; Laws 1967, c. 242, § 1, emerg. eff. May 5, 1967.