5.1 The letters shall be capital letters in Roman characters
without ornamentation. Numbers shall be Arabic numbers
without ornamentation.
5.2 The width of each character (except the letter I and
the number 1) and the length of hyphens shall be two-thirds of
the height of a character.
5.3 The characters and hyphens shall be formed by solid
lines and shall be of a colour contrasting clearly with the background.
The thickness of the lines shall be one-sixth of the
height of a character.