The license tax imposed by sections 3.466 and 3.467 shall not be imposed on any motor vehicle fuel sold to the Armed Forces of the United States for use in ships, aircraft or for export from the city – but every dealer shall be required to report such sales to the tax administrator in such detail as may be required. A certificate by an authorized officer of such Armed Forces shall be accepted by the dealer as sufficient proof that the sale is for the purpose specified in the certificate.