Underprint

An underprint is anything printed underneath the main design of a stamp, banknote or similar item.

Underprinting is used as a security measure to prevent forgery, or the cleaning of a postmark from a used stamp.

Underprinting may also take the form of single or repeating words, for instance the word CUSTOMS at one time appeared underprinted on British revenue stamps.

[2] The term has also been used in philately to refer to advertising or other wording printed on the back of postage stamps.

[3] However, this is thought to be an incorrect[4] use of the term, with the word backprint being seen as more correct.