If any of the underwriters applying for certificate of authority hereunder is not a citizen of the United States, each such alien underwriter shall, at the time of the making of the aforesaid application for certificate of authority, deposit with the Insurance Commissioner the sum of five thousand dollars ($5,000) in cash, or in securities such as are now required for the investment of the capital of insurance corporations authorized to do similar kinds of insurance business in this Commonwealth, or in such kinds of securities as may be approved by him. The provisions of this section as to deposits shall not apply if such alien underwriter is one of an association of underwriters having on deposit with the insurance department of any State of the United States, or in the hands of a bank or trust company as trustee, a cash deposit or approved securities, worth not less than one hundred thousand dollars ($100,000), held in trust for the benefit of all their policyholders in the United States; nor shall this section as to deposits apply if such alien underwriter is one of an association of underwriters nine-tenths of whom are at all times citizens of the United States, and who have complied with all other provisions of this act.