172. Whenever, under this Act or any ¹[rule or regulation] made hereunder, the doing or the omitting to do anything or the validity of anything depends upon the approval, sanction, consent, concurrence, declaration, opinion or satisfaction of- (a) the Kartripakkha or the Chairman, or(b) any employee of the Kartripakkha, a written document, signed, in case (a) by the Chairman, and in case (b) by the said employee, purporting to convey or set forth such approval, sanction, consent, concurrence, declaration, opinion or satisfaction, shall be sufficient evidence of such approval, sanction, consent, concurrence, declaration, opinion or satisfaction.