Every licensee shall keep in his cold storage the agricultural produce of one hirer separate from such produce of other hirer and from other produce of the same hirer for which a separate receipt has been issued, so as to permit at all times the identification and easy delivery thereof :
Provided that where standardized and graded goods are stored in the cold storage, the same variety of goods belonging to the same or different hirer may, subject to any contract to the contrary, be pooled together and each hirer shall be entitled only to his portion of the goods according to weight or quantity as the case may be, as shown in his receipt, less any driage or shrinkage up to the limit fixed under Explanation to section 17.