Hello,
in the WIKIPHIL section, you will find information, but especially photos of stamps which are very unusual and sought after by "ASFE" collectors (A Stamp From verywhere) also called Geophilatelia or collection of 1 stamp - 1 country.
Classification from A to Z according to the inscription on the stamp, according to the alphabet used (Greek, Cyrillic, Arabic, etc.) and of course with the file of "UNKNOWNS" stamps.
Regarding the "UNKNOWNS" any information from you will be welcome.
https://timbre.sk/en/4396-wikiphil