Actually yes, I did find something from under the seat lug. Unfortunately, it was a sticker from the company that's originally sold the bike.
(Edit: not necessarily the original resaler, but under the paintjob anyway.)

BUT, it's a good thing that you got me into this!!


I had to use a high power flashlight to see what I'm doing. This actually, besides helping mee see the disappointing sticker under the seat lug, also helped me to realize, that the frame has indeed been re-painted!! ​ Actually, the decals on the seat tube and the down tube have just been covered and the frame has been painted with an ever so slightly darker shade of blue. This can also be seen at some places where the paint has flaked but the frame hasn't yet started gathering rust...


Well, as you suggested, I think I'll just go and pick some random dark blue color and have the frame painted with that. Or with some other color? You never know, clearly there's nothing worth saving so I can let my imagination run wild...