No corporation not now authorized to transact business in this state shall be licensed to transact the business of life or casualty insurance, or both, upon the cooperative or assessment plan, until at least 300 persons eligible to membership have made individual applications, in writing, containing warranties of age, health, and other required conditions of membership, and the corporation has on deposit with the commissioner, as security for all its policyholders, stocks or bonds of this state or of the United States, or bonds of any of the municipalities of this state, or personal obligations secured by first mortgage on real estate within this state, worth, exclusive of buildings, the amount of the lien, and bearing interest of not less than three percent per annum, to an amount the actual market value of which, exclusive of interest, shall never be less than $100,000; provided, that any corporation which has heretofore procured and filed with the commissioner a part of the total number of applications required by law shall only be required to deposit securities of the market value of $5,000; and provided, that a corporation that confines its membership exclusively to the members of volunteer fire departments shall be required to have not less than 100 individual applications, in writing, from persons eligible to membership and the sum of at least $1,000, which amount shall be liable only for death or indemnity claims made under its policy or membership certificate contracts.