No notice of the expiration of the time of redemption upon any real estate tax judgment sale certificate, forfeited tax sale certificate, or state assignment certificate heretofore issued pursuant to any law of this state at or pursuant to any such sale held in the year 1935 or prior thereto, which has not become void under any law, shall issue or be served after the expiration of six months from the date Laws 1941, chapter 399, becomes effective; nor shall such certificate be recorded in the office of the county recorder or filed in the office of the registrar of titles of the proper county after December 31, 1942.