Awesome article, @Tapp! And learned some new things as well, including that the English ones were distributed in the US. 
It’s also curious how the English ones have N3X as code; the French FB5; and the German and Italian GF6.
Thanks to this thread from earlier this year, we now know those EX era codes can be used on a Japanese mobile app Pokemon Hiroba to see close-up pictures of the artwork (if you have internet access). Not too useful if you’d ask me, since you usually have the card in hand if you have a code, but whatever. Likely they intended more uses for the codes in that mobile app over time, but since 2003 wasn’t exactly a smartphone era yet, almost no one used it.
Greetz,
Quuador