Proof of consent of Board or Chairman or officer or other employee of Board.

Whenever, under this Act or any rule or regulation made thereunder, the doing or the omission to do anything or the validity of anything depends upon the approval, sanction, consent, concurrence, declaration, opinion, or satisfaction of—

1. (a) the Board or the Chairman, or
2. (b) any officer or other employee of the Board, a written document signed by the Chairman, in case of item (a) and by the said officer or other employee in the case of item (b), conveying or setting forth such approval, sanction, consent, concurrence, declaration, opinion or satisfaction, shall be sufficient evidence of such approval, sanction, consent, concurrence, declaration, opinion or satisfaction.