Links to detailed listings of Philatelic Terms
1. Ask Phil. Excellent  and exhaustive listing of terms.
2. Linns List of Stamp Terms.

The below listing of descriptions of philatelic terms is limited to those pertinent for the Silver Jubilee issue. A more detailed listing can be obtained from the links above.

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Albino: Used to describe a complete un-inked impression. An example is when two sheets are fed in at the same time. The un-inked sheet receives an indented impression. When this sheet is “re-printed” with ink, two impressions may be seen, the inked and the un-inked impressions. This has been described with the Falkland Islands albino or double albino impressions.
Aniline Colour: Aniline is a water-soluble dye in the red colour range. It is derived from coal tar. The colour tends to suffuse through the stamp and shows though on the back of the stamp to a much greater extent than normal. If the stamp is examined under a quartz (Ultra-violet) lamp it fluoresces.
Arrow Block: An arrow-like shape that is found in the selvedge of a block of stamps. It was used as a guide indicating a convenient spot to either cut or fold the sheet of stamps.

Backstamp: A postmark applied to the back of an envelope

Cachet: An added design or text to a cover, either printed, embossed or handstruck. It is usually added to indicate a special event or the special circumstances for posting the letter or item e.g. a First Day Cover.
Cinderella Stamp: A stamp-like label that is not issued for postal purposes but is affixed to the cover or postal item.
Colour Trials: Proofs of a stamp taken using a variety of colours (single or in combination). This allows the postal agency to decide which colours to select for the issued stamp.
Control Letters: Letters inscribed in the sheet margin (selvedge). Found primarily amongst British Stamps. The control letter also includes two numerals indicating the last two digits of the year of issue.
Cylinder Numbers: These are tiny numbers engraved on the cylinder and appear in the sheet margin (selvedge). British Stamps are usually printed in pairs and are similarly numbered. The right sheet pane is distinguished from the left one by the presence of a dot after the number.

Die: The original piece of metal on which the stamp's design is first engraved.  Reproductions are made from the die and used to produce the printing unit.
Die Proof: An impression taken from the original die and placed on special paper. It is used to check that all the detail on the die is correct.
Doctor Blade: A special flexible steel blade that is used to remove surplus ink from the printing cylinder. Doctor blade flaws appear as non-constant lines on printed stamps.
Duty Plate: This plate is used when there are two or more steps in the printing of a stamp. It is used to print the value or the name of the country/colony and value on the stamp. The other plate used is the Key Plate.

Erased: Removal of a portion of a design in order to modify it. The extra-flagstaff erased (Bradbury Plate 1 Row/Column 9/1) is an example.
Essay: A design submitted for a stamp. It denotes that the stamp was either not adopted or it was adopted after alterations to the original submission were made.
Exploded Booklet: A stamp booklet that has been taken apart so that the individual panes, including the interleaving pages and covers, can be fully displayed.

Frame: That part of the stamp that encloses the central portion of the stamp. In the omnibus Silver Jubilee issue the frame encloses the portrait of King George and the central vignette of Windsor Castle.

Guidelines and Dots: Fine lines or dots that are marked on the plate as a guide for the engraver when transferring impressions. Normally these are removed but can sometimes be visible in the selvedges.

Hair Lines: Fine colorless scratches from a printing plate.

Imprimatur: Final authorization (usually has word "approved") marked on final colour plate proofs.
Impression: Term used for the mark or picture on the printed sheet as a result of the pressure from the printing press or plate. This is the actual printed design of a stamp.
Imprint: This is the name of the printer (or issuing authority) and usually appears in the selvedges.
India Paper: Thin, tough, opaque absorbent paper used commonly for printing engraved proofs.
Intaglio: A type of printing technique. In this technique ink lies in the recesses of the plate and the paper is forced into them taking up the ink. Also known as line-engraving, recess-printing and photogravure.

Key Plate: This is the plate that prints the general stamp design. The term is used when two or more separate printings are required. The other plate used is the Duty Plate.

Marginal Guide: These are lines, dots, arrows or other marks found in the margins (selvedges) of the sheets of stamps. The printer used them as a guide in trimming or perforating the stamps.

Omnibus Issue: The issue of a uniform stamp design simultaneously by several countries to commemorate an event or person.

Paquebot: Mail posted aboard a ship. The mail was then usually mailed ashore at the next port of call even though the stamp used may not be from that country.
Perforation Guide Boxes: Three sided 'boxes' printed in the margin - used as guide for
guide holes.
Photogravure: A photo-mechanical version of intaglio printing.
Plate: Material, usually metal, from which the stamp is printed. The plate can be flat, curved or cylindrical in shape. The first plate made is called the Master Plate and may not be actually used for printing. Reproductions made from it are called Working Plates.
Plate Proof: An impression taken by the printer prior to printing the sheets. Its purpose is to check for flaws or errors.

Re-entry: Duplication of part of a line-engraved (intaglio printed) stamp design due to inadequate erasure of the original modification to the design.

Selvedge: The margins or marginal paper surrounding a sheet of stamps. Sometimes spelt as Selvage.
Strip: Three or more un-separated stamps from the same columns or rows. Unless clearly defined, it implies a `horizontal' rather than a `vertical' strip.

Tête-bêche: Philatelic term indicating a pair of stamps in which one is upside-down in relation to the other.
Toning: Discoloration on covers or stamps caused by exposure to light, heat, humidity, air or a combination of these factors.
Transfer Roller: The steel roller, used in intaglio printing, which transfers the image from the master die to the plate.

Value Tablet: The panel or space on a stamp stating the declared monetary face value of the stamp.
Variety: A stamp that visually differs from other stamps undergoing the same printing process.
Vignette: The central or main portion of the stamp.