How were Harappan seals and sealings ued to facilitate long distance communication? What did the sealings convey?

Explanation

(i) The bag of goods to be sent from one place to another and was tied its mouth with a rope and knot was affixed some wet clay on which more seals were pressed to leave an impression.
(ii) The sealings conveyed: (a) the bag reached with the sealing intact, not tempered, (b) the identity of the sender.