Excise duty

In february 2012 ,The govt. has retrospectively reduced the prices of coal w.e.f. 1.1.2012. For the payment of excise duty, for coal removed in  the month of january 2012,  which price shall be considered - original or reduced price?

In my opinion it should be based on original price since any change in the price of goods after its removal is irrelevant for the purpose of excice duty as per Supreme Court in case of MRF.