To minimize counterfeiting, banks have developed various security features on banknotes.
Watermark, security thread, holograms are easily recognizable, but there are also micro-letters.
These micro-letters are invisible to the naked eye and present us with simple lines or patterns, they are nevertheless of strings forming words or even sentences.
This type of protection requires a magnifying glass magnification X5 least on some tickets to be checked. For example on German banknotes, it is necessary to use a X10 magnification.
More micro prints are small they are more difficult to print
Here is an example of what we can read on the notes of the last range of french's Bank note
We can say without any exaggeration that until the beginning of this century, the branch of physics on the air resistance does not present confusion and uncertainty.
The French flag is the only one who has a staff of three hundred meters. - Gustave Eiffel
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