s 11 Where duty chargeable depends on duty paid on another instrument
Where the duty with which an instrument is chargeable, or its exemption from duty, depends in any manner upon the duty actually paid in respect of another instrument, the payment of such last-mentioned duty shall, upon application to the Collector for that purpose and production of both the instruments, be denoted upon such first-mentioned instrument by indorsement under the hand of the Collector or in such other manner, if any, as may be prescribed by rules made under this Act.