Cal. Ins. Code § 10159.2

After December 31, 1943, any insurer may file with the commissioner a written notice of its election to comply with the provisions of this article as to any or all of its policies after a specified date before January 1, 1948. After the filing of such notice, then upon such specified date, this article shall become operative with respect to the policies specified in the notice and which are thereafter issued by such insurer. As to all of its policies with respect to which an insurer makes no such election, the operative date of this article shall be January 1, 1948.