
Shipmail
The objective of shipmail is the transport of mail by means of commercial vessels: liners, cargo boats, ferries, scientific ships (in Antarctica) ... Here are some examples of such covers.

letter with the label «Posted at sea» on the liner France and illustrated slogan to right of date stamp from Le Havre

Letter posted aboard the liner FRANCE (see reverse) and postmark SOUTHAMPTON paquebot

Reverse side of letter
Clicking on the image reveals the other side of the envelope