I’m pretty sure the Jigglypuff isn’t distinguishable between the original 1996 and 2k 1998 release either, a.f.a.i.k.
Only the Pikachu is, due to the corrected illustrator Keiji Kinebuchi on the 2k release from 1998, which was the wrong illustrator Ken Sugimori on the original 1996 release.
If you know how to distinguish between the two Jigglypuff releases, I’m curious to know.
The only Glossy reprints that I know can be distinguished, are the ones from the Pokémon Best Song CD:
But I don’t think the Pikachu, Jigglypuff, Mew, Mewtwo, Flying Pikachu, etc. can be distinguished that way, since all magazine promos were peelable in a similar matter a.f.a.i.k.
Greetz,
Quuador