First Day of Issue - Earliest Known Use

The earliest known use (EKU) of a stamp may or may not be the same as the first day of issue. This can occur if:

• Stamps are inadvertently sold or stolen, and cancelled on an envelope or package by unaware postal officials prior to the first day of issue.
• Minor changes, such as a different perforation, are noted by postal officials, and no one knows when they first went on sale. This is also true of some major stamp issues, especially during periods of civil unrest or if government records have been lost.
• Some earlier stamps, especially high values, have not found any customers using them on the day of issue, or those uses have been lost. EKUs for these may be weeks or even months after the official first day.
• Some stamps have not have had an officially designated first day of issue and instead were simply placed on sale whenever the stamps were needed.

The search for EKUs of both old and new stamps is an active area of philately, and new discoveries are regularly announced.