The board shall appoint and fix the compensation and duties of a director, an assistant director, a secretary, and a chief curator of the National Gallery of Art, and of such other officers and employees of the National Gallery of Art as may be necessary for the efficient administration of the functions of the board. Such director, assistant director, secretary, and chief curator shall be compensated from trust funds available to the board for the purpose, and their appointment and salaries shall not be subject to the civil-service laws or chapter
51 and subchapter
III of chapter
53 of title
5. The director, assistant director, secretary, and chief curator shall be well qualified by experience and training to perform the duties of their office and the original appointment to each such office shall be subject to the approval of the donor.