Where physical or mental examination is required of an applicant for National Service Life Insurance or of an applicant for reinstatement of National Service Life Insurance, such examination may be made by a medical officer of the United States Army, Navy, Air Force, or Public Health Service, or may be made free of charge to him or her by a full-time or part-time salaried physician or a physician's assistant at a regional office or medical facility of the Department of Veterans Affairs. Such examination may also be made, at the applicant's own expense, by a physician duly licensed for the practice of medicine by a State, possession of the United States, Commonwealth of Puerto Rico, or the District of Columbia, or by a duly licensed osteopathic physician who is a graduate of a recognized and approved college of osteopathy and who is listed in the current directory of the American Osteopathic Association. Such examination may be made by a physician or osteopath who is not related to the applicant by blood or marriage, associated with him or her in business, or pecuniarily interested in the insurance or reinstatement of the policy. Examinations made in a foreign country by a physician duly licensed for the practice of medicine and otherwise acceptable may be accepted if submitted through the American consul. The Secretary of Veterans Affairs may require such further medical examination or additional medical evidence as may be deemed necessary and proper to establish the physical and mental condition of the applicant at the time of the application.