Earliest known use or EKU: The cover or piece that documents the earliest date on which a stamp or postal stationery item is known to be used. New discoveries can change an established EKU. The EKU for a classic issue may be after the official issue date. Because of accidental early sales, the EKU for modern stamps is often several days before the official first day.
Embossing: The process of giving relief to paper by pressing it with a die. Embossed designs are often found on the printed stamps of postal stationery (usually envelopes and wrappers). Selected stamps of certain countries have been embossed.
Encased postage stamp: A stamp inserted into a small coin-size case with a transparent front or back. Such stamps were circulated as legal coins during periods when coins were scarce.
Entire: An intact piece of postal stationery, in contrast to a cutout of the imprinted stamp. This term is sometimes used in reference to an intact cover or folded letter.
Error: A major mistake in the production of a stamp or postal stationery item. Production errors include imperforate or imperforate-between varieties, missing or incorrect colors, and inversion or doubling of part of the design or overprint. Major errors are usually far scarcer than normal varieties of the same stamp and are highly valued by collectors.
Essay: The artwork of a proposed design for a stamp. Some essays are rendered photographically. Others are drawn in pencil or ink or are painted. Most essays are rejected. One becomes the essay for the accepted design.
Etiquette: A gummed label manufactured for application to an envelope to designate a specific mail service. Airmail etiquettes are most common.
Europa: The “United Europe” theme celebrated annually on stamps of western European nations since 1956. The original Europa stamps were issued by the nations in the European coal and steel association. Today, European nations that are members of the postal and telecommunications association (CEPT) issue Europa stamps.
Expertization: The examination of a stamp or cover by an acknowledged expert to determine if it is genuine. As standard procedure, an expert or expertizing body issues a signed certificate, often with an attached photograph, attesting to the item’s status.
Exploded: A stamp booklet that has been separated into its various components, usually for purposes of display. Panes are removed intact: individual stamps are not separated from the pane.
Express mail: Next-day mail delivery service.