In my search, to make a complete (?) list of all countries, territories, and states, ... that have issued stamps, I came up so far with 375 different entries.
Some stamps are issued by an organisation, like the United Nations.
They aren't really belonging to a country, unless you consider the territory of the UN in New Your, Geneva or Vienna, as being an independent country.
Therefor I have listed such stamps under a new category.
After I sorted out all countries to their continents (using 1 to 5), I made a new list starting with 6...
(0)60201 = UN New York
(0)60301 = UN Geneva
(0)60401 = UN Vienna
(0)60501 = UN Interim Administration in Kosovo
Some stamps were issued related to suborganisations of UN, and I have given them an individual number as well, for those who collect themewise stamps related to UN.
(0)60901 = International Labour Organisation (ILO)
(0)60906 = UNESCO
(0)60910 = UPU
and so on
A bit similar, but yet different is my 7th category.
These are stamps issued by existing countries, but for a special purpose, like the CEPT-stamps I posted before.
CEPT is only one type of European stamps that are emitted by several countries, before 1956, a cooperation existed between the Belgian, Dutch and Luxemburgian gouvernment, forming BE-NE-LUX.
Older belgian catalogues mention a number of stamps that are related to a specific european theme.
Like 'balcan cooperation, 'baltic cooperation', 'NATO', 'EFTA' and so on.
Therefore, I made a list of those 'themes' as they are collected in Europe.
I will post more on those specific themes later. As for now, I have plenty to post about the CEPT issues.