The bonds of the authority shall be signed by its president or vice-president and attested by its secretary, and the seal of the authority shall be affixed thereto; provided, that a facsimile of the signatures of said officers may be printed or otherwise reproduced on any such bonds in lieu of manual signatures thereon, and a facsimile of the seal of the authority may be printed or otherwise reproduced on any such bonds in lieu of being manually affixed thereto.