(a) Any employer subject to Article III and who shall desire to become a subscriber to the fund for the purpose of insuring his liability to his employes; and any employer who wants insurance under the Longshore and Harbor Workers' Compensation Act (44 Stat. 1424, 33 U.S.C. § 901 et seq.); and any employer who wants insurance under the Federal Coal Mine Health and Safety Act of 1969 (Public Law 91-173, 30 U.S.C. § 801 et seq.) and who shall desire to become a subscriber to the fund for the purpose of insuring his liability to his employes; and any employer who shall desire to become a subscriber to the fund for the purpose of insuring therein his liability for all sums the employer shall become legally obligated to pay any employe of his as damages because of bodily injury by accident or disease, including death at any time resulting therefrom, sustained by such employe arising out of and in the course of his employment, shall make a written application for such insurance to the board. In the application, the applicant shall state:

(b) When the employments are subdivided into classes, as provided in section 1510,¹ the applicant shall state:

(c) Upon submission of the application, the board shall make such investigations as it may deem necessary and, within thirty (30) days after the application, shall issue a certificate showing the classification or group in which such applicant is entitled to be placed and the amount of premium payable by such applicant for the year for which insurance is sought. No insurance shall be issued for a longer period than a single year.