Fluorescent Postmark Impression of Franking Machine
Phosphorescent and fluorescent stamps were invented in Britain
in 1959. These stamps were introduced as security feature for anti-forge
purpose and they could also be compatible with the automatic mail
sorting machines. The stamps coated with the phosphorescent or fluorescent
ink would emit special colours (such as red, green, blue.etc.) under
ultraviolet light. In 1960, Pitney Bowes, an American company began
to initiate the research on using fluorescent ink for postmark impression
of franking machine. In 1972, the company secured the contract from
the United States Postal Services and conducted a test. The result
showed that the mails with fluorescent postmark impression could
be handled by the automatic mail sorting machine same as those affixed
with normal stamps. As this arrangement could better enhance the
work efficiency, the fluorescent postmark impression of franking
machine have been widely adopted since 1 July 1973 in the USA (see
picture 1). The postmark of this letter was originally in blue,
under the ultraviolet light, red fluorescent is emitted, and Pitney
Bowes' fluorescent ink usually emits an orange colour.
Nowadays, most franking machines in Hong Kong are with fluorescent
postmark impression. Simply put your mail with fluorescent franking
impression under ultraviolet light, you would discover something
interesting. (Article supplied by The China Philatelic Association)
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