A member of the Board who is not otherwise an employee of the United States is entitled to receive pay at the daily equivalent of the annual rate of basic pay of the highest rate of basic pay under the General Schedule of subchapter III of chapter 53 of title 5, for each day the member is engaged in the performance of duties vested in the Board, and is entitled to travel expenses, including a per diem allowance, in accordance with
section 5703 of title 5.