India
Under Certificate of Posting

This aerogramme (Wiegand no. 40)) was sent from CALCUTTA to Sheffield, UK.

In India, any unregistered postal items could be posted under certificate of posting, which worked as a proof of posting. Usually, the sender prepared a list of the items to be mailed under the certificate and affixed stamps to pay for the certificate. The post office clerk, then, confirmed the acceptance of the items by cancelling the stamps paying the certificate's fee with a date stamp.

This service was discontinued in 2011.

References
Wiegand stands for Wiegand, Katalog der Aerogramme von Asien, 2000