Illustrated Glossary

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Earliest Documented Cover - (EDC)

The earliest documented cover is becoming the preferred way to collect early usages of U.S. stamps, partly because a cover tells much more of the story behind the early usage. Many texts are beginning to make this distinction. Determining the earliest documented cover is a difficult task, particularly since the information is not kept in an easily available format and in some cases the information is not shared.

Earliest Documented Use - (EDU)

This term is often used interchangeably and incorrectly with "Earliest Known Use". It refers to the earliest date, documented by expert opinion, for which a stamp is known to have been used. We have included the "Earliest Documented Usage" for many of the classic issues in the U.S. by Year pages. The distinction between EDU and EKU is an important one, since many of the earlier reported EKUs have proven to be incapable of verification. By definition, "documented" means the stamp/cover has been expertized by one of the expertization agencies.

Edison Issue

A 1929 U.S. commemorative issue celebrating the 50th anniversary of the invention of the electric light bulb.

EE Bars

(Electric Eye Bars) These bars aid the electric eye in the perforating process. EE bars are commonly found in the margins of sheet stamps, but are usually trimmed from coil stamps; the plate block at right has the EE bars in the left margin. The term "EE" refers to the fact that the stamps were perforated using the electric eye method.


An acronym for "Errors, Freaks and Oddities".

Electric Eye

In 1933, starting with the two-cent stamp, the US Bureau of Engraving and Printing began experiments to improve the perforation process. The plate block at right is from one of the first electric eye plates ever printed. Note the position of the plate number, it's not in the corner as rotary press plate numbers normally are. The electric eye makes use of a photovoltaic cell employing a beam of light to aid in perforation accuracy. Although the experimental sheets had a series of dashes down the very center of the sheet and a single dash in the center of the left margin, the electric eye markings we are familiar with were not added to the sheet margins until 1939. The philatelist may note that many stamps after 1940 always seem to be well-centered. The electric-eye had a large part in this.

Electric Eye Dashes

On the 400 subject sheets, 41 vertical dashes were added to the vertical gutter between the right and left panes to aid the electric eye in the perforating process. There were two vertical dashes per stamp and a single vertical dash dead center between the upper and lower panes.

Electric Eye Horizontal Frame Bars (Frame Slugs)

Horizontal lines in the left sheet margin were used to aid the electric eye in the perforating process. This marking was first used in the US in 1939.

Embossed Printing (Relief Printing)

The design of an embossed stamp is raised on the transfer roll, as opposed to the recessed design on the engraved plates, with the resulting image pressed into the paper, rather than being placed on top of the paper as in the engraving process. Note that ink is not necessary for embossing purposes.

Endwise Coil

Coil stamps linked together endwise, that is the top of one stamp is connected to the bottom of the next. These are more often referred to as "vertical coils". Note that endwise (vertical) coils are perforated horizontally.

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.

Engraved (Intaglio)

The engraving printing method allows ink to settle into the engraved lines of the plate. In wet printing, which was common until the 1950s, wet paper is pressed into the grooves thus transferring the ink to the paper, in a sense placing the ink on the surface of the paper. This resulted in the ink being slightly raised, a fact which is immediately apparent when one rubs a finger across the surface of the engraved stamp.

Engraving Process

The process by which the stamp's design is cut into a metal die. The design is then transferred to the "transfer roll" and finally to the printing plate.


This usually refers to any complete, intact cover.


A gummed label used on an envelope to designate a specific mail service; airmail etiquettes are most common.


The "United Europe" theme which has been 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.


Errors are a special group that are often given separate listings. The most famous U.S. errors are the inverts, for example the upside down airplane, but the term also applies to imperforate stamps that were intended to be perforated, or perforated stamps that have an improper perforation, as well as stamps missing a color or colors. Lack of tagging when the stamp should be tagged is also considered an error, and is analogous to a missing color error. What distinguishes "errors" from their cousins, the freaks and oddities, is that an error must be a major production mistake.

Errors, Freaks and Oddities

A general term for stamps and envelopes that have irregularities of some form. "Errors" are major production mistakes. "Freaks" encompass a wide range of unusual variations, including color or perforation shifts, while "oddities" encompasses an even wider range of variations, including over- or under-inking, foldovers, or any other factor that makes the stamp look odd.


A design or any artwork officially proposed (essayed), as the design for a stamp. An essay is a stage in the design of the stamp that was not adopted in the final design. Thus an essay differs from the design of the issued stamp. This is to distinguish it from a "proof" which is identical in design to the issued stamp.


The process by which an expertizing service renders an authoritative opinion on the genuineness of a stamp and cover.

Express mail

Inaugurated in 1977, expedited or next-day mail delivery service in the United States.

Exploded Booklet

A booklet that has been broken into its component parts, usually for display purposes.