31. (1) No commercial weight or measure or weighing instrument or measuring instrument shall be sold, delivered, used or possessed for use in any transaction of trade or commerce unless it has been verified and stamped in the prescribed manner: Provided that where, in the case of any commercial weight or measure or any class thereof, compliance with the requirement of this section is not, in the opinion of the Government, practicable, the Government may, by notification in the official Gazette, exempt such weight or measure or class from such requirement. (2) Where any commercial weight or measure or weighing instrument or measuring instrument-(a) is found in the possession of any trader or any employee or agent of any trader, such trader, employee or agent shall be presumed, until the contrary is proved, to have had it in his possession for use in transaction of trade or commerce; and(b) is used or possessed by any employee or agent or any trader on behalf of the trader, such trader shall, unless he proves that it was used or possessed by the employee or agent without his knowledge or consent, be also deemed to have used it or to have had it in his possession.