law: Indian Stamp Act, 1899 
  22. Effect of statement of rate of exchange or average
  
  price 
  Where an instrument contains a statement of current rate of
  
  exchange, or average price, as the case may require, and is stamped in
  
  accordance with such statement, it shall, so far as regards the subject-matter
  
  of such statement, be presumed, until the contrary is proved, to be duly
  
  stamped.