[(5) The provisions of this section shall not apply to any decision or order in which the determination of any question having a relation to the rate of duty of excise or to the value of goods for the purposes of assessment of any duty is in issue or is one of the points in issue.
Explanation.—For the purposes of this sub-section, the determination of a rate of duty in relation to any goods or valuation of any goods for the purposes of assessment of duty includes the determination of a question