01
Stamp anatomy
- Perforation gauge · perfs
- The series of small holes punched between stamps on a sheet to enable individual separation. Introduced in Britain in 1854 (replacing the scissors-cut imperforate issues from 1840). The perforation gauge — the number of holes per 2cm — is a critical identification factor. A standard perforation gauge (Instanta or Gibbons gauge) is essential equipment for the serious collector; many variety and catalogue distinctions depend on gauge differences.
- Watermark paper security mark
- A pattern or device formed in the paper during manufacture by a dandy roll, visible when the stamp is held to the light. Watermarks were used as a security feature and to distinguish stamp paper from ordinary paper. Changes in watermark design create distinct catalogue varieties — the same stamp design on different watermarked papers may have very different values. A watermark detector tray (with watermark fluid) is needed for opaque stamps.
- Gum adhesive · original gum
- The adhesive applied to the reverse of a stamp for affixing to mail. Original gum condition is a major grading factor for unused stamps: original gum never hinged (OG NH or **) is the highest condition; original gum with hinge remnant (OG HR or *) indicates a former hinge; regummed (RG) stamps have had new gum applied, which significantly reduces value. Gum types changed over time: early gums were gum arabic; modern gums are synthetic.
- Selvage margin paper
- The unprinted border paper surrounding the printed stamp area on a sheet. Selvage may carry sheet numbers, dates, imprints, traffic lights (colour registration marks), or printing information. Plate numbers in the selvage (particularly on US stamps) create the "plate block" collecting specialty. Stamps with selvage attached are "marginal copies" — those at the corner of a sheet are "corner copies."
- Plate number printing plate identifier
- A number printed in the sheet margin identifying the specific printing plate used. Important for Great Britain line-engraved stamps (1840–1880) where the plate number also appears within the stamp design as a corner letter code. Plate number collecting is a major specialty — some plate numbers are rare, and certain plate numbers had very small printings.
- Colour shade · printing colour
- The precise colour of a stamp's printing, which can vary significantly between different printings and papers. Colour shades are documented in specialist shade guides and listed separately in catalogues when they represent distinct printings. Many major rarities are shade varieties — the "olive-green" versus "olive-bistre" distinction can represent a tenfold value difference.
02
Printing methods
- Line engraving / Recess printing intaglio · engraved
- The printing method used for the world's first adhesive stamps — the Penny Black (1840) and early issues of many countries. The design is engraved (cut) into a steel die; ink is pressed into the recesses and transferred to the stamp paper. Recess-printed stamps have a characteristic raised feel to the design, detectable by touch. The engraved lines also show under magnification with greater clarity than lithographed stamps.
- Letterpress / Typography surface printing · relief printing
- A printing method in which ink is applied to the raised surface of the plate (the reverse of engraving). Used for many British surface-printed stamps from the 1850s onward. Letterpress can be identified by slight embossing on the reverse of the stamp and by the characteristic appearance of the ink, which tends to fill corners of letters slightly.
- Lithography flat printing · photolitho
- A printing method based on the chemical incompatibility of grease and water, using a flat limestone or metal plate. Early stamps (particularly German states, Switzerland) used hand-drawn stone lithography; modern photolithography uses photographic reproduction. Lithographic stamps tend to have slightly less sharp lines than engraved stamps.
- Photogravure gravure · rotogravure
- A rotary adaptation of recess printing using a photographic positive to expose the image onto a cylinder. The process allows finer detail and faster production than line engraving. Used widely from the 1930s onward; many mid-20th-century British stamps are photogravure. Gravure stamps are identifiable by their characteristic dot pattern under magnification.
- Embossing relief printing without ink
- A stamping process that creates a raised (embossed) design without ink. Used on early British stamps (embossed shilling stamps, 1847) and some revenue stamps. The design is raised on the stamp face and depressed on the reverse. Pure embossing without colour is unusual and distinctive; most embossed stamps also incorporate an ink border.
03
Varieties & errors
- Colour error wrong colour · colour variety
- A stamp printed in a markedly different colour from the standard — either through use of the wrong ink, misregistration of printing cylinders, or paper absorption differences. Major colour errors are among the most valuable philatelic rarities. Minor shade varieties are much more common and command smaller premiums.
- Imperforate unperforated · between / on two/three sides
- A stamp that lacks perforations, either as an issued variety (before 1854 in Britain, some issues elsewhere) or as an error (a perforate stamp left unperforated through machine failure). Imperforate pairs are collected as proof that both stamps lack perforations — a single imperforate could theoretically be a perforated stamp with perfs cut off.
- Inverted centre / Misprint invert · major error
- A stamp where one element of the design (typically the centre vignette in a two-colour stamp) was printed upside-down relative to the frame. The most famous is the US 24-cent Airmail of 1918 with an inverted Curtis JN-4 biplane (the "Inverted Jenny"). Genuine major errors are extremely rare; collectors should be sceptical of any offered at below-market prices.
- Overprint variety surcharge variety
- A stamp with a handstamped or typographed overprint (changing its value or use, or commemorating an event) that shows a variety — an inverted overprint, a double overprint, a missing overprint. Overprint varieties are extensively documented; some are extremely rare and valuable while others are relatively common.
- Coil stamp roll stamp · vending machine stamp
- Stamps issued in roll form for use in vending machines or affixing machines, with straight edges on two sides (top and bottom or left and right). Coil stamps often have specific perforations — typically straight edges on two opposing sides — distinguishing them from sheet stamps of the same design. Coil singles, pairs, and strips are collected.
04
Cancellations
- Circular Date Stamp CDS · town cancellation
- The standard postal cancellation — a circular handstamp containing the town name and date. A clear, readable CDS on a stamp is generally preferred for used copies, as it confirms the stamp's genuine postal use and may provide dating information. Stamps with complete, legible town and date CDS are described as "fine used."
- Squared circle postmark c. 1880 – 1930 · British
- A distinctive cancellation combining a circular date stamp within a square border, used by the British Post Office from approximately 1884 to 1932. Squared circle postmarks are a specialist collecting area; the town, date, and "duplex" number within the circle help identify the specific office. Collecting matched pairs of stamps and postmarks from the same town and date is a refinement of the specialty.
- Slogan cancel advertising cancel · machine cancel
- A cancellation incorporating a slogan or promotional message alongside the wavy-line machine cancellation. "Post Early for Christmas," military recruitment slogans, and commercial advertising are common examples. Slogan cancels add historical interest to used stamps and are collected in their own right, separately from the stamps they cancel.
- First Day Cover FDC · first day of issue
- A postal cover (envelope) bearing a stamp or set of stamps cancelled on the first day of their issue. Collected since the late 19th century; became formally recognised and widely collected from the 1930s. First Day Covers are collected with cachets (decorative printed designs relating to the stamp's theme) and with town cancellations from the place of issue.
- Revenue cancellation pen cancel · fiscal cancel
- Revenue (fiscal) stamps — used to pay taxes rather than postal fees — are typically cancelled by pen or handstamp rather than by a postal machine. Revenue cancellations range from simple pen marks to ornate manuscript cancels. Pen-cancelled stamps are typically worth less than postally used stamps, but revenue cancellations on revenue stamps are appropriate and correct.
05
Condition
- Mint / Unmounted Mint MNH / ** · finest condition
- An unused stamp with complete original gum, never hinged. The finest condition for an unused stamp; mint stamps command significant premiums over hinged or disturbed gum examples. The term "unmounted mint" (UMM) or "never hinged" (NH) is used in British and American catalogues respectively; double asterisk notation indicates this grade in Stanley Gibbons.
- Fine Used FU · neatly cancelled
- A used stamp with a neat, legible cancellation that does not obscure the design and does not damage the perforations. Fine used is the preferred condition for many collectors of used stamps. Light, centrally placed cancellations command premiums; heavy or smudged cancellations, pen cancellations, or cancellations that cover the design are devalued.
- Catalogue to Order CTO · cancelled by agreement
- Stamps cancelled by the issuing postal authority before sale — typically using a light, attractive cancellation — and sold directly to dealers for resale to collectors. CTO stamps are generally worth less than postally used stamps of the same issue; some specialists refuse to collect them.
- Space filler poor condition example
- A stamp in below-standard condition — with faults such as thin paper, tears, creases, short or missing perforations, or heavy cancellations — kept as a placeholder in an album until a better example can be acquired. A space filler has minimal market value but serves a practical purpose in completing a collection.
- Fault defect
- Any physical damage to a stamp that reduces its grade: tears, thins (where paper has been removed, typically by hinge removal), creases, missing perforations, short perforations, soiling, staining, or ink loss. Faults must be disclosed in any honest description; faulty stamps are worth 10–50% of fault-free examples depending on scarcity. For common stamps, faults reduce value dramatically; for extreme rarities, a faulty example may still command a significant price.
06
General terms
- Philately the study and collection of stamps
- The study and collection of postage stamps and related postal materials — postmarks, covers, postal stationery, and fiscal stamps. From the Greek philos (loving) and ateles (free from charge — the original stamps paying postage). The world's first philatelic society was the Philatelic Society London, founded in 1869; major national philatelic societies exist in every stamp-issuing country.
- Definitive regular issue · workhorse stamp
- A stamp designed for everyday postal use, typically printed in large quantities over long periods. Definitives carry the same design over many years, with changes in colour, watermark, or perforation creating the catalogue varieties that specialist collectors pursue. The British Machin definitive (introduced 1967) is the most-printed stamp in history.
- Commemorative special issue
- A stamp issued for a limited period to mark a specific event, anniversary, or theme — as opposed to a definitive. Commemoratives typically have higher face values and shorter print runs. They are produced in smaller quantities than definitives and are the primary target of most general collectors. First day covers are almost exclusively produced for commemorative issues.
- Se-tenant joined different designs · connected stamps
- Two or more stamps of different designs that are printed adjacent to each other on the sheet and must be collected together. Se-tenant pairs, strips, and blocks are typically collected as multiples; separating the stamps reduces their value. Common in modern commemorative issues; also found in some classic-era stamps where different values were printed together.
- Miniature sheet souvenir sheet · sheetlet
- A small sheet containing one or more stamps, usually with a decorative margin. Miniature sheets are often issued alongside the normal sheet stamps. They may have different perforations or formats than the sheet versions; in some cases the stamp in a miniature sheet is only available in that format. Miniature sheets are highly popular with collectors.
- Catalogue value SG / Scott / Michel value
- The value assigned to a stamp by a standard catalogue — Stanley Gibbons (British emphasis), Scott (American emphasis), or Michel (German and European emphasis). Catalogue values represent approximate retail prices for fine examples; actual market prices may be significantly higher or lower. The ratio between catalogue value and market price varies considerably by country, period, and condition.