If, before the effective date of this section, a bank or its predecessor in interest, has caused a safe-deposit box to be opened for nonpayment of rental, and the contents of such box or any part thereof remain in its custody, it shall be entitled to the special remedies in enforcing the liability of the former renter of such box as set forth in Sections 1634 to 1639, inclusive, whether or not such box was rented prior to October 1, 1949.