11The fixing of the seal of the corporation shall be authenticated by the signature of the chairman or of some other member authorised either generally or specially by the corporation to act for that purpose.
12Any contract or instrument which, if made or executed by a person not being a body corporate, would not be required to be under seal may be made or executed on behalf of the corporation by any person generally or specially authorised by them to act for that purpose.
13Any document purporting to be a document duly executed under the seal of the corporation shall be received in evidence and shall, unless the contrary is proved, be deemed to be so executed.