First of all. If I am not mistaken, all posters in this topic are from Switzerland, right? So, go back in your memories. When I saw the post of HB-IGG, it reminded me, that some years ago in Switzerland many series of alphanumeric registrations didn't have the "J". I can't recall any example, but I noticed it already elsewhere. Evenmore: do you remember how "J" was spelled at school? Depending on the school, this letter was named "Joggeli I" or however else. This letter isn't used very much in our language.
Now, Perhaps the guy at the aviation administration (BAZL) has been fired and they have now a young guy, who sees the difference between an "I" and an "J".
Regards and "Es Grüessli"
dominguez(dash)online(dot)ch ... Pushing the limits of my equipment