IBI - see Identification Based Indicia.

Identification Based Indicia - a commercial product which is a computer generated, postage paying, stamp-like imprint authorized by the USPS.

Illegal Use - an illegal use of a stamp, such as a revenue stamp used in an attempt to pay postage.

Image Tagging - the tagging of only the image (design) or a portion of the image on a stamp.  Examples: 1988 25¢ Classic Autos (Scott 2381-2385); 1999 33¢ American Glass (Scott 3325-3328).

*Imperforate - stamps without perforations.  The earliest stamps were issued in imperforate form.  Imperforate stamps that were intended to be perforated are errors.

Imprint - design containing the name of the producer of the stamps, which appears on the sheet margin, usually near the plate number.

Imprint Block - a margin block of stamps, analogous to a plate block, which contains an imprint instead of a plate number.

In-line Perforator - a perforating device included in the mechanized portion of a printing press, automatically activated as the printed web or sheets pass through the station.

India Paper - a thin, tough, translucent paper used for making die proofs.

Indicia - plural of indicium.

Indicium - 1) the stamp-like impression on postal stationery,  2) the imprint of postage made by a postage meter.

Ink-Jet Cancel - a dot matrix cancel also known as a Sprayed-on Cancel.

Instructional Marking - see Auxiliary Marking.

Insured Mail - mailed articles insured for a fee by the Postal Service.

*Intaglio - a process of printing from the recessed portion of a printing plate.  See also engraving

Intagliocolor 8 Press - high-speed, three-color, sheet-fed  intaglio press used at the BEP from 1976 to 1985.

Integral - a device that applied initials, date, and precancel simultaneously.

Integrated Retail Terminals - Computers in post offices that weigh items, calculate postage, print receipts and maintain records.

Interleaves - sheetlets of glassine paper placed between panes in stamp booklets.

International Envelope Corporation - manufacturer of early and mid-twentieth century stamped envelopes and wrappers.

International Mail - mail sent from the United States to a foreign nation or sent from a foreign nation to the United States, as opposed to Domestic Mail.

International Philatelic Exhibition - one in a series of international stamp shows hosted once every decade in the U.S.  Held in New York City in 1926, the Battle of White Plains stamp and souvenir sheet (Scott 629 & 630) were issued in conjunction with this show.

International Postal Supply Company - major manufacturer of cancelling machines in use from the 1880s into the 21st century.

International Reply Coupon - a coupon sold by the post office that is redeemable by its recipient in a foreign country for return postage.  Scott catalogue numbers are prefixed with IRC.

International Vending Machine Company - Baltimore-based manufacturer of vending machines and private coils.

International Vending Machine Company Perforations - perforations privately applied to imperforate  flat plate  stamps by the International Vending Machine Company for use in its vending machines.

Interphil '76 - one in a series of international stamp shows hosted once every decade in the U.S.  Held in Philadelphia in 1976, a stamp (Scott 1632) was issued to honor Interphil '76.

Interrupted Mail - mail that has been delayed by some external event such as a plane or train crash, war, fire, etc.

*Invert - a stamp or item of postal stationery on which one portion of the design is upside down in relation to the rest of the design.  Inverts can only be produced when the production process requires at least two independent passes through a press.  Inverts are errors.

Inverted Jenny - nickname for the 24¢ air mail  error  stamp of 1918 on which the airplane (vignette) was printed upside down in relation to the frame.  Scott C3a.

Involute Flag Cancel - a flag cancel in which the flag is folded.

IRC - see International Reply Coupon.

Irradiated Mail - mail irradiated by the U.S. Postal Service during the anthrax terrorism of 2001-02.

IRT - see Integrated Retail Terminals.

Italian Occupation Issues - see Allied Military Government Stamps.

J               

Jeffries Banknote Company - subcontractor to American Banknote Co.. for the 1991 $14 postage stamp (Scott 2542).

Jenny - see Inverted Jenny.

Joint Issue - stamps issued by two or more countries simultaneously, with similar designs, honoring the same person or event.  Example: 1975 Apollo-Soyuz Space Issue, Scott 1569-1570.

*Joint Line - the printed line produced on the web by the rotary press at the point where two plates met.  Two plates were used in combination with each other on the classic rotary press.  Each plate would fit over half of the printing cylinder.  Ink would gather in the joints between the plates, leaving an impression (a joint line) on the web.  One complete revolution of the press cylinder created two joint lines on the web.  Joint lines were produced on both sheet and coil stamps, but only those produced on the coil stamps are commonly collected.  A Joint Line is not the same as a Guide Line.

Joint Line Gap Pair - A joint line pair of precancelled coil stamps that shows the gap between the auxiliary plates used to print the precancel.

*Joint Line Pair - a pair of coil stamps produced from the rotary press with a joint line between them.  A joint line pair will contain one stamp from each of two different plates.  See also Joint Line.

Junk Mail - nickname for advertising send by bulk rate mail.

K               

K - prefix letter used by KCS Industries in front of the plate number on its modern stamp production.

Kansas City Roulettes - improvised perforations applied by roulette to imperforate 1¢ and 2¢ postage stamps (Scott 408 and 409) by the postmaster of Kansas City in 1914 and 1915.

*Kansas-Nebraska Overprints - Series of 1922 postage stamps overprinted "Kans." or "Nebr." in 1929 for sale in those states, but valid in all states.  Scott 658-679.

KCS Industries - private printer and finisher of postage stamps.  Example: non-denominated Tulip booklet of 1991 (Scott 2520).

Killer Cancel - a cancellation that is very heavy, obliterating most of the design of a stamp.

Knife - 1) the pattern used to cut an envelope from a sheet of paper.  2) the device that cuts stamps apart as they are fed through an affixing machine.

L               

L perforator - an L-shaped manually fed perforating machine on which stamps receive horizontal perforations on one leg of the L and vertical perforations on the other.

Label - a stamp-like adhesive of no postal value, often used for promotional purposes.  Christmas Seals are examples of labels.  "Label" may also be used to describe the stamp-like units that bear messages that sometimes appear in stamp  booklets.

Laid Paper - paper with the appearance of alternating dark and light lines, created by wires used in the paper making process.   Similar to but less pronounced than ribbed paper.   Example:   2¢ Jackson of 1863 (Scott 73).

Large Bank Notes - postage stamps produced from 1870-1888 by the National, Continental and American Banknote Companies (Scott 134-218).  See also Small Bank Notes.

Large Die Proof - a die proof printed on card stock that is considerably larger than the image created by the die, as opposed to a Small Die Proof.  The die print on a Large Die Proof is located in a recess on the card known as a sinkage.

Large Holes - perforation holes that are larger than other perforations holes of the same gauge.  For example, Scott 1055 in the Liberty Series exists with perforation holes of two different sizes (large and small) even though all are perforation gauge 10.  Compare: Small Holes.

Last Day of Sale - 1) the day a stamp is removed from sale by the Postal Service.  2) a slogan cancellation applied to stamps on the last day of sale.  A "Last Day of Sale" cancellation was used for the first time on March 16, 1997.

Late Fee - 1)  payment required for mail accepted for dispatch (usually on a particular ship) after the closing of the mails.  2) a Supplementary Mail Marking applied to Supplementary Mail.

Laundry Tags - two-sided address cards used on suitcase-like containers (mostly by college students) to mail dirty laundry home to be cleaned and returned.

Layout Marks - dots, lines and arcs that are scribed by a siderographer on a blank plate to determine the precise location for each entry to be made from the transfer roll.

Leader - a strip of brown kraft paper (white paper beginning in 1948) attached to the leading (first) stamp on a roll of coil stamps.

Leavitt, Thomas - major manufacturer of cancelling machines in use from the 1870s to the 1890s.  Leavitt cancelling machines were the first to receive extensive use.

Legends of Hollywood - series of commemorative stamps honoring famous Hollywood personalities.  The first stamp in this series is the 1995 Marilyn Monroe (Scott 2967).

*Legends of the West - a pane of twenty stamps that was recalled because an incorrect picture appeared on the stamp honoring Bill Pickett (Scott 2870).  A limited number of recalled panes was sold by public lottery.  The corrected version (Scott 2869) was then printed and issued.

Letter Sheet - an item of postal stationery similar in format to an aerogram.  Example: Scott U293.  Privately produced letter sheets exist.

Letterpress - a process of printing which is the exact opposite of intaglio, that is, the inked portion of the plate is raised above the surface of the plate, as opposed to be being recessed below it.  Letterpress (also see typography) has been used to print overprints on U.S. stamps.  It is also used in perfecting (back printing) inscriptions on the gum of many stamps, and to print most modern stamped envelopes.

*Liberty Series - definitive series of postage stamps appearing in 1954, consisting of sheet stamps, coils, and booklets.  Also known as Sixth Bureau Issue.  First Scott number is 1030a.

Library Mail Rate - special rate for mailing certain materials to or from certain non-profit organizations, a sub-category of Package Service.  Commercial libraries could also use this rate as long as the contents were suitable (books, motion pictures, etc.).

Line Engraving - see Engraving.

Line Gaps - the gap between plates printing precancels that appears on coil stamps at regular intervals.

Line Pair - see Joint Line and Guide Line.

Line Perforator - A perforator that applies lines of perforation holes in only one direction.

Liner - slick paper used as peelable backing for self-adhesive stamps.

Linerless Coil - self-adhesive  coil stamps sold in a roll without a liner.  Example: 1997 32¢ Flag over Porch stamp, Scott 3133.

*Literary Arts Series - series of commemorative stamps honoring important American writers, begun with the John Steinbeck stamp of 1979, Scott 1773.

Lithography - printing from a smooth surface on which the area that is not to be printed repels the ink.  One form of lithography is direct lithography, in which printing occurs without the use of an intermediate roller or blanket.  Some early Post Office Seals were printed from such direct lithography.  Indirect lithography uses an intermediate roller or blanket, and is called offset.  See also Offset Lithography.

Little America - the Antarctic base of Admiral Richard Byrd that was home to a special post office, for which Scott 733, the “Little America Issue", was released in 1933.  Covers bear a Little America postmark.

LL - Lower left.  Refers to the lower left pane from a traditional sheet of four panes.  These initials are also used to describe plate blocks taken from the lower left corner of the sheets.

Local Letter - a letter mailed within a city at a rate sometimes less than the regular first class rate.  Such local letters are of two types: those mailed in cities with carrier service and those mailed in cities without carrier service.  Some form of local letter rate was in existence from 1863 to 1968.  See also: Drop Letter.

Local Post - a private postal system operating in a limited area, usually a major city.  Example: Hussey’s Post, New York, N.Y.  Local posts once played a significant role in mail delivery.

Local Precancel - a precancel applied to stamps locally, as opposed to being applied at the Bureau of Engraving and Printing.  See also Bureau Precancel.

Local Stamps - stamps issued by private companies operating in limited service areas.  Most of these stamps were issued by companies operating in a single city, but local stamps were also issued by independent mail routes and express companies.   Scott numbers contain an L.

LOOK Coil - phosphor tagged version of the 3-cent Statue of Liberty coil in the 1954 Liberty Series, issued without advance notice in October 1966 for use on LOOK Magazine promotional mailings.  Use by LOOK Magazine was limited to about a six month period, after which the stamps were recalled, marking the first time the U.S. Post Office Department bought stamps back from the private sector for distribution to collectors.  Tagging applied by rubber mats and glows brightly under ultraviolet light.  See also LOOK Coil Reprint.

LOOK Coil Reprint - a special printing of the LOOK Coil made to satisfy collector demand.  The reprint became a new variety because the BEP applied the tagging by metal plates.  The tagging on the reprint glows duller and grainier under ultraviolet light than the tagging on the original LOOK Coil.

*Louisiana Purchase Exposition Stamps - commemorative  postage stamps issued for the St. Louis Exposition of 1904.  Scott 323-327.

Lozenges - the bi-colored border frequently found on air mail postal stationery.

LR - Lower right.  Refers to the lower right pane from a traditional sheet of four panes.  These initials are also used to describe plate blocks taken from the lower right corner of the sheets.

Luminescence - the light given off by fluorescent brighteners and phosphorescent tagging in paper and ink when activated by ultraviolet light.

*Lunar New Year Series - series of twelve postage stamps honoring the Chinese New Year.  The first of the series is Scott 2720, issued in 1992.