Cover (philately)

The term does not include the contents of the letter or package, although they may add interest to the item if still present.

[1][2] The term originates from the practice of covering a letter by folding a separate sheet about it to physically protect it and prevent infringement of confidentiality.

Its convenience and popularity led to the lozenge design being adopted for the special pre-paid postage envelopes and covers issued in 1840 after postal reforms were introduced by Rowland Hill and others.

[3] A philatelic cover is an envelope or post card prepared with a stamp(s) and address and sent through the mail delivery system for the purpose of creating a collectible item.

Patriotic cover availability here can vary also depending on the country and time period in question.