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, including Scott, are beginning to make this distinction. Although, we are making an effort to make the most current information regarding earliest documented covers and usages available on this web site, this is a difficult task, particularly since the information is not kept in an easily available format and in some cases the information is guarded jealously. If you have any information that supercedes any listed date on this site, we, and the stamp collecting community, would be most grateful for such updates. Our records reflect EDUs and EDCs through 2003.

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 three expertization agencies.

Earliest Known Use - (EKU) The first date for which a stamp is reported to have been used. Note that many U.S. stamps had official release dates, but occasionally a post office released the stamp before that release date. These early usages are not regarded as EKUs, they are known as pre-dates.

EDC - an acronym for "Earliest Documented Cover ". A stamp with an EDC of the issue date is known as an FDC or First Day Cover.

Edison Issue - (Scott's 645-656) a 1929 U.S. commemorative issue celebrating the 50th anniversary of the invention of the electric light bulb

EDU - an acronym for "Earliest Documented Use"

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.

EFO - an acronym for "Errors, Freaks and Oddities"

EKU - an acronym for "Earliest Known Use"

Electric Eye - In 1933, starting with the two-cent stamp, Scott 634, the 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 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.


Engraved (Intaglio) - The engraving method allows ink to settle into the engraved lines of the plate. In wet printing, which was common until the 1950’s, 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. 

Engraver - the craftsman who engraves the image of the stamp on a die

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.

Entire - On this web site, "entire" refers to any intact cover.

Error - Errors are a special group that are often given separate Scott Catalog listings. The most famous U.S. errors are the inverts, for example the upside down airplane Scott C3a, 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.

Essay - 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.

Expertization - the process by which an expertizing service renders an authoritative opinion on the genuineness of a stamp and cover.
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Exploded Booklet - a booklet that has been broken into its component parts, usually for display purposes.