Each insurer shall maintain at its home or principal office a complete file containing a specimen copy of every printed, published or prepared advertisement of its individual policies and specimen copies of typical printed, published or prepared advertisements of its blanket, franchise and group policies, hereafter disseminated in this state, with a notation indicating the manner and extent of distribution and the form number of any policy advertised. Such file shall be subject to inspection by the insurance commissioner. All such advertisements shall be maintained in said file for a period of either four years or until the filing of the next regular report on examination of the insurer, whichever is the longer period of time.