As I am new in this Community, some of my first messages got edited by the staff. So they are rather strange as missing sense, now. I will try to explain in SCF acceptable terms.
Collecting one stamp from every stamp issuing entity is known as ASFE = A Stamp From Everywhere. I have a specialized club ASFE Slovakia. The link was edited, but simply to find.
On the site there is the 780 ASFE stamp issuing entities updated list, which is based on 780 entities as described in the 2 books in English I have published. The books originate from Czechoslovakia....I have updated the list.


There are also over 80 articles I have writtten on ASFE theory and many hard to find territories. They are in Slovak language, but translation is easy with translator, plus there are hundreds of scans, so easy to undertand. And you still have a chance to consult me, if needed.
ASFE collectors work with wanlists (or havelists), so that they can cooperate. My wantlist is published there, other wantlists are welcome. They are important, as the more wantlists we have, the more precise is the list of hard to find stamps. My articles are usually about them.
Cordoba is one of the hardest to find ASFE items from the original list, but not the top one. On the top there are Chorezm and postal Bokhara. Naturally the updated list is much harder to collect - there are Kotah, Tonk....to mention just a few ones discussed here.
And one important note - ASFE collectors collect also local stamps and BOB stamps, which are usually 99% of wantlists of advanced ASFE collectors. My favorites are Great Bitter Lake Associations (GBLA) stamps, about which I have opened a new topic.