There shall be filed with the commissioner by such attorney a statement under oath showing the maximum amount of indemnity upon any single risk, and such attorney, as often as the same is required, shall file with the commissioner a statement verified by his oath to the effect that he has examined the commercial rating of such subscribers as shown by the reference book of a commercial agency having at least one hundred thousand subscribers and that from such examination or from other information in his possession it appears that no subscriber has assumed on any single risk an amount greater than ten percent of the net worth of such subscriber.