There is created the National Portrait Gallery Commission. The number, manner of appointment and tenure of the members of the Commission shall be such as the Board may from time to time prescribe. The Board may delegate to the Commission any function of the Gallery or any function of the Board with respect to the Gallery. The Board may make rules and regulations for the conduct of the affairs of the Commission and the operation of the Gallery, and to the extent and under such limitations as the Board deems advisable, the Board may delegate to the Commission the power to make such rules and regulations.