Underprint: A fine printing underlying the design of a stamp, most often used to deter counterfeiting.
Ungummed: A stamp without gum. Ungummed stamps are either stamps issued without gum or an uncanceled gummed stamp that has had its gum soaked off. Many countries in tropical climates have issued stamps without gum.
Unhinged: A stamp without hinge marks, but not necessarily with original gum.
Universal Postal Union: An international organization formed in Bern, Switzerland, in 1874, to regulate and standardize postal usage and to facilitate the movement of mail between member nations. Today, most nations belong to the UPU.
Unused: An uncanceled stamp that has not been used but has a hinge mark or some other characteristic or defect that keeps it from being considered a mint stamp. Uncanceled stamps without gum may have been used and missed being canceled, or they may have lost their gum by accident.
used: A stamp or stationery item that has been canceled by a postal authority to prevent its reuse on mail. In general, a used stamp is any stamp with a cancel or a precanceled stamp without gum. See also Postally Used and Philatelic Cover.
UPU: Universal Postal Union. An international organization formed in Bern, Switzerland, in 1874, to regulate and standardize postal usage and to facilitate the movement of mail between member nations. Today, most nations belong to the UPU.
Want list: A list of needed stamps or covers, identified by catalog number or some other description, submitted by a collector to a dealer, usually including requirements on condition and price.
Water-activated adhesive: Stamp gum designed to adhere to envelope paper only if the gum is moistened. All gummed stamps before 1963 used water-activated adhesive.
Watermark: A deliberate thinning of paper during its manufacture to produce a semitranslucent pattern. Watermarks appear frequently in paper used in stamp printing or envelope manufacture. See also Batonne.
Web: A continuous roll of paper used in stamp printing.
Wing margin: Early British stamps from the side of a pane with selvage attached. British sheets printed before 1880 were perforated down the center of the gutter, producing oversized margins on one side of stamps adjacent to the gutter. Such copies are distinctive and scarcer than normal copies.
Wove paper: A paper showing few differences in texture and thickness when held to light. In the production of wove paper, the pulp is pressed against a very fine netting, producing a virtually uniform texture. Wove paper is the most commonly used paper in stamp production.
Wrapper: A flat sheet or strip open at both ends that can be folded and sealed around a newspaper or periodical. Wrappers can have an imprinted stamp or have a stamp attached.
Zemstvo: A local stamp issued by Russian municipal governments or zemstvos, in accordance with an imperial edict of 1870.
Zeppelins: The stamps issued for, or in honor of, zeppelin flights. Cacheted covers carried on such flights are Zeppelin covers.
ZIP block: “U.S. marginal marking block with the selvage bearing the image of the “”Mr. ZIP”” cartoon character and/or an inscription urging the use of ZIP code. This first appeared on U.S. marginal selvage in 1964. Typically a ZIP block is a block of four stamps.”
ZIP code: The U.S. numerical post code used to speed and mechanize mail handling and delivery. The letters stand for Zoning Improvement Plan.
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