Section 2L
Stock aud m rt kdczble sccuiz/Ics lzow f.J ht v zlllcrf \Vhere an ' in<>trument is chargeable with ad valonm duty in respect of any stock or of any marketable or other security, such duty shall be calculated on the value of such stock or security according to the average price or the value thereof on the day of date of the instrument.