I picked up two sealed copies of the Endless Night theme deck to investigate/verify the coins that came inside.
This deck is from a trio of decks released for Great Encounters.
The other two decks feature Dialga and Palkia coins that are respectively blue and pink and that much the legendary Pokemon on the box art of the deck. There were no Darkrai coins released back in Gen IV so there was no obvious coin to match/include with this theme deck.
I received two different coins inside the two sealed decks.
On Bulbapedia, these two Dialga and Palkia coins have previously been attributed to Great Encounters blister packs and a different Palkia coin was attributed to this theme deck.
While it is possible that these two coins were also included in the Great Encounters blisters, I suspect that either:
a. The other Palkia coin is attributed in error
b. OR a different print run of this deck used different coins
That other Palkia coin is known to be from Diamond & Pearl blister packs so it is strange that it would get re-used for this deck.
These two coins are extremely difficult to find online and, in fact, I’ve never before seen a copy of the Dialga coin that is this clean nor have I seen a photo of either coin actually appear in a sealed product.
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My opinion is now that these two coins were intended to be included with this theme deck and that the other Palkia coin is either a typo or is a third/alternate configuration for this deck that I do not have.
Either way, I’m happy to have confirmed at least one product that these coins appeared in. Its possible that they did appear in Great Encounters blister packs but I’ve yet to see photos of this.