20. (1) The Government may make rules, for the purposes of this Act, to provide, with respect to any goods which purport or are alleged to be of uniform number, quantity, measure, gauge or weight, for the number of samples to be selected and tested and for the selection of the samples.(2) With respect to any goods for the selection and testing of samples of which provision is not made in any rules for the time being in force under sub-section (1), the Court or officer of Customs, as the case may be, having occasion to ascertain the number, quantity, measure, gauge or weight of the goods, shall, by order in writing, determine the number of samples to be selected and tested and the manner in which the samples are to be selected.(3) The average of the results of the testing in pursuance of rules under sub-section (1) or of an order under sub-section (2) shall be prima facie evidence of the number, quantity, measure, gauge or weight, as the case may be, of the goods.(4) If a person having any claim to, or in relation to, any goods of which samples have been selected and tested in pursuance of rules under sub-section (1) or of an order under sub-section (2), desires that any further samples of the goods be selected and tested, they shall, on his written application and on the payment in advance by him to the Court or officer of Customs, as the case may be, of such sums for defraying the cost to the further selection and testing as the Court or officer may from time to time require, be selected and tested to such extent as may be permitted by rules to be made by the Government in this behalf or as, in the case of goods with respect to which provision is not made in such rules, the court or officer of Customs may determine in the circumstances to be reasonable, the samples being selected in manner prescribed under sub-section (1), or in sub-section (2), as the case may be.(5) The average of the results of the testing referred to in sub-section (3) and of the further testing under sub-section (4) shall be conclusive proof of the number, quantity, measure, gauge or weight, as the case may be, of the goods.(6) Rules under this section shall be made after previous publication.