History of the Euro Oval
The UN convened
in 1969 to create an easy way to
identify the different sources of traffic in Europe and other
places. That meeting reulted in the declaration of adding a sticker to your vehicle
with a country code, so that officials could easily identify your origin.
Here is the
official text below from the US's Convention on Road Traffic in
DISTINGUISHING SIGN OF VEHICLES IN INTERNATIONAL TRAFFIC
distinguishing sign shall be composed of one to three letters in
capital Latin characters. The letters shall have a minimum height of
80 mm. (3.1 in.) and their strokes a width of 10 mm. (0.4 in.). The
letters shall be painted in black on a white ground of elliptical
form with the major axis horizontal.
If the distinguishing sign is
composed of three letters, the dimensions of the ellipse shall be at
least 240 mm. (9.4 in.) in width and 145 mm. (5.7 in.) in height.
The dimensions may be reduced to 175 mm. (6.9 in.) in width and 115
mm. (4.5 in.) in height if the sign carries less than three letters.
As regards the distinguishing signs for motorcycles, the dimensions
of the ellipse, whether the sign is composed of one, two or three
letters, may be reduced to 175 mm. (6.9 in.) in width and 115 mm.
(4.5 in.) in height.
3. The distinctive letters for the
different States and territories are as follows:
See here for full list of country codes
Any State which has not already done so shall on signature or
ratification of, or accession to, this Convention, notify the
Secretary-General of the distinctive letters selected by that State.
4. When the distinguishing sign
is carried on a special plate this plate shall be fixed in a
vertical or nearly vertical position and in a plane perpendicular to
the longitudinal axis of the vehicle itself. When the sign is fixed
to or painted on the vehicle itself, this shall be done on a
vertical or nearly vertical surface at the back of the vehicle.