I guess I can start off with saying that full yellow WOTC era blanks were printed specifically for playtesting. These were made during the localization process to make sure translation/localization did not affect gameplay. They were asked to just toss them in the trash after playtesting was done. According to Mr. Ryan, nobody really thought much about them. He only had a small stack from cleaning out his desk upon leaving WOTC/Pokemon.
I mean for U.S I know that they had little slips of paper on yellow cardstock but those are kinda obsolete and the only way to get one would of been to ask an employee who randomly had a couple I think Leonhart made a video featuring them
This is one of the ones from Leonhart’s Videos you mentioned!
The card originally came from Michael Ryan, former Director of Editing for WOTC. Leonhart bought a chunk of his collection including this and a few other Playtest cards.
Leonhart did a couple videos about Michael and his collection including an interview. I learned about these first when Leonhart did his Card Party video and he got them back from CGC.
After that I reached out Leonhart about selling one. Since the market was unknown, we settled on auctioning one on Rare Candy, which is where I won this one.
Those videos, stories, and how it all went down personally gives me full confidence in the card. The kind of information and tranparency that should come with cards like these.