112. An affidavit of a member or a member of the staff of the board attesting that he is entrusted with the appropriate registers and that a document annexed thereto is a document or true copy of a document, made by or on behalf of the board or any other person acting on behalf of the board, or by or on behalf of a person subject to this Act, is proof of the nature and content of the document, until proof to the contrary, and must be allowed as proof and has the same probative force as the original document if its accuracy had been proved in the ordinary manner.