Agencies which transacted business and exercised powers prior to September 15, 1961, shall, in any proceeding involving the validity of, or enforcement of, or relating to, any contract by an agency, be conclusively deemed to have been established and authorized to transact business and exercise its powers upon proof of the adoption of a resolution adopted pursuant to the provisions of this part which were in effect prior to September 15, 1961, or upon proof that a copy of such resolution has been filed with the Secretary of State.