1. Any person who has had twelve months' service on deck at sea or on the Great Lakes on any vessel of 100 tons gross and upward (except those navigating rivers exclusively and the smaller inland lakes, and except fishing or whaling vessels or yachts), including decked fishing vessels, naval vessels, and coast-guard vessels, may make application to any board of local inspectors for a certificate of service as able seaman, and upon proof being made to said board by affidavit as to service, and examination as to physical condition and knowledge of the duties of seamanship, showing the nationality and age of the applicant and the vessel or vessels on which he has had service, the board of local inspectors shall issue to said applicant a certificate of service which shall be retained by him and be accepted as prima facie evidence of his rating as able seaman. 2. No person shall be examined who does not produce satisfactory affidavit or affidavits that he has served at sea or on the Great Lakes as prescribed in paragraph 1. 3. Each applicant shall pass the prescribed physical examination before a medical officer of the Public Health Service before being permitted to take the examination to determine his knowledge of the duties of seamanship. 4. The professional examination to determine the applicant's knowledge of the duties of seamanship shall be oral, and shall be conducted in the form of questions and answers and by practical tests. The applicant shall be examined in each of the prescribed subjects and given a mark in each based on a scale of 100. 5. No person shall be recommended for or shall receive the certificate of service as able seaman who fails to attain a general average of merit of 70 per cent. 6. The professional examination may be conducted by an officer of the United States Navy, the Coast Guard, Lighthouse Service, Coast and Geodetic Survey, Navigation Service, or any other marine officer designated by the Secretary of Commerce. When any such officer conducts the examination the board of local inspectors shall issue to the applicant a certificate of service as able seaman upon receiving notice in writing from such an officer that the applicant has passed the prescribed examination as to the knowledge of the duties of seamanship. 7. The professional examination will be conducted as concisely as possible, with the view of determining the applicant's qualifications, and will embrace the following subjects: (_a_) _Boxing the compass._—The applicant will be required to box the compass by points or degrees, according to the experience he has had in the use of either method. (_b_) _Lights and fog signals._—A knowledge will be required of the running and anchor lights for steam and sailing vessels on the sea, inland waters, or Great Lakes, and a like knowledge of fog signals, according to the waters on which the applicant has served.