If an auction house does cite a source, I’m fairly positive they will use E4 as a reference. I am absolutely certain that an auction house couldn’t find out the history of a card if even the members of E4 are stumped. Like @eeveeteam says, the information is here if any where.
I believe the first reference of this ‘learn to play’ was from the sale of a Charizard. These two posts in particular;
This blog post also compiles the majority of information found within this thread and others into one regarding E1.
There’s many threads to read on here about E1 unlimited, as I’m sure you’re well aware of already. There is a lot of information within these posts to dissect, some of them speckled with loose translations or speculation and others will have some truth. Possibly conflicting statements could be both true if there were multiple distribution methods or it’s possible people don’t recall exactly what happened.