Tagging is the phosphor coating on stamps used to activate automatic mail-handling equipment. This may be lines, bars, part of the design area or the entire stamp surface. Some stamps are issued both with and without tagging. Catalogues call them tagged and untagged.
In some cases, the tagging is omitted in error.
light is usually required to identify tagged
stamps, but with experience you may be able to
detect the tagging under normal lighting conditions
by holding the stamp at an angle to a light source.
The first tagging in Canada appeared in 1962 on
the 1c-5c low-value Wilding
definitives. This tagging was called 'Winnipeg
tagging' because it was introduced and tested in
Winnipeg, Manitoba. Winnipeg tagging is
phosphorescent bars applied vertically - 1-bar
(left, centre and right) or 2-bar. The difference
number of bars was to distinguish between local and
forward mail. Winnipeg tagging was discontinued in
Winnipeg tagging reacts to ultraviolet light and
will leave an afterglow when the ultraviolet light
source is removed.
Starting in April 1972, 'General tagging' was
introduced in Ottawa, Ontario and has since become
the norm. Initially, two types existed: OP-4 and
OP-2. The former migrates and can spread onto
other stamps. It was used only on stamps printed by
General tagging was initially applied in vertical
bands down the perforations (giving us 2-bar
tagging). Two stamps, the 88c and 90c Fruit Trees
definitives appeared with 3-bar tagging (an
experiment for international mail). It is now the
norm to have stamps tagged on all 4 sides. This
allows the machinery to detect the tagged stamp
regardless of whether the stamp is affixed to the
envelope vertically or horizontally.
General tagging fluoresces when exposed to
ultraviolet light and has a yellow-coloured
Phosphor - 'invisible' ink (tagging) applied to the front of the stamp in vertical bars (one, two, or three have been used on Canadian stamps) or around all four sides of the stamp that, when exposed to ultraviolet light, activates a sorting and canceling machine.
Canada issued its first phosphor tagged
stamps in 1962 in readiness for the installation
of a British-made letter-facing machine in
General tagging - phosphor tagging
introduced in April 1972 in Ottawa, Ontario.
fluoresces a yellow-colour when exposed to ultraviolet
light. Two major types exist: OP-4 and OP-2 (the
former migrates, or spreads, throughout the
stamp and will bleed onto and through other paper
that is in prolonged contact with the tagging).
Winnipeg tagging - the name given to the phosphor tagging
introduced on January 13, 1962 due to the city where
it was used: Winnipeg, Manitoba. An ultraviolet
light is required to detect these.
Click for a large UV-light image of the 3c, 4c and 5c Wilding Winnipeg-tag stamps. Note that Winnipeg tagging can be a bit difficult to view; sometimes it may be seen under regular lighting when viewed at an angle.
UV lamp - ultra-violet lamp used for the detection of fakes, forgeries and phosphor tagged stamps.