@quuador has a great thread with pictures of lots of obscure cards including the Japanese sample cards: www.elitefourum.com/t/pokemon-tcg-picture-dump/17973/1.
There’s also a thread here all about the unlimited E1 set: www.elitefourum.com/t/japanese-unlimited-e-series-1-cards-base-expansion-pack/16426/1. It’s gotten quite long so if you want a condensed version of everything we know so far I’ve written a blog article about the set: pichu.blog/unlimited-e1.
The unlimited E1 tl;dr is that we currently believe the cards were distributed as part of a lottery event at participating Pokémon Gym stores (here’s the section on my blog which discusses that: pichu.blog/unlimited-e1#pok%C3%A9mon-card-gb2-lottery-event).