¹[31. The rate of duty applicable to, and the rate of exchange for computation of the value of, any goods exported shall be the rate of duty or, as the case may be, the rate of exchange prevailing on the date of the delivery of the bill of export under section 131: Provided that where the export of any goods is permitted without a bill of export or in anticipation of the delivery of such a bill, the rate of duty applicable to, and the rate of exchange for the computation of the value of, such goods shall be the rate of duty or, as the case may be, the rate of exchange applicable on the date on which loading of the goods on the outgoing conveyance commences.]