I did this one from memory... I might have forgotten one or two countries. The only mistake I've found so far, is that I painted Argentina. I have a postcard coming from Buenos Aires, but I haven't actually received it yet.
The map is too small to paint other countries (and territories with their own postal authorities) that I have as well, like Luxemburg, Vatican City, Cape Verde 🇨🇻, Liechtenstein 🇱🇮, Bermuda 🇧🇲, Fiji 🇫🇯, Macau 🇲🇴, Bahrain 🇧🇭, the Åland Islands 🇦🇽 and others