(1) All bonds or other evidences of debt having a fixed term and rate held by any insurer may, if amply secured and not in default as to principal or interest, be valued as follows:

(a) If purchased at par, at the par value.

(b) If purchased above or below par, on the basis of the purchase price adjusted so as to bring the value to par at the earliest date callable at par or maturing at par and so as to yield in the meantime the effective rate of interest at which the purchase was made; or in lieu of such method, according to such accepted method of valuation as is approved by the commissioner.

(c) Purchase price shall in no case be taken at a higher figure than the actual market value at the time of purchase.

(d) Unless otherwise provided by a valuation established or approved by the National Association of Insurance Commissioners, no such security shall be carried at above call price for the entire issue during any period within which the security may be so called.

(2) Such securities not amply secured or in default as to principal or interest shall be carried at market value.

(3) The commissioner shall have full discretion in determining the method of calculating values according to the rules set forth in this section, and not inconsistent with any such methods then currently formulated or approved by the National Association of Insurance Commissioners.