#78p looks to be a promo for Pokemon Battle Trozei, a 3DS eShop only game developed by Genius Sonority and released in 2014. Likely the reason why the back looks like it has a blurb about the game and how to purchase it on the eShop.
Here’s an old product listing for it on a site and also the Yveltal version. Also looks like there were stickers in the usual flat square style as well.