Prices are changing fast on this one, so it's worth keeping an eye on
Number 686 Language English Legal Formats Alchemy, Brawl, Commander, Competitive Brawl, Historic, Legacy, Modern, Pioneer, Standard, Timeless, Vintage Rulings (7/12/2019) Cryptic Caves can be one of the five lands you control
Barring some exceptions, Japanese booster packs typically have five cards instead of ten, like the English packs
The best way to perform this test is to compare the suspect card to a basic land from the exact same set
While Wizards owns a lot of the IP on Magic cards (the art, mana symbols, etc.) there is t nothing illegal about a piece of cardboard the same size of a Magic card with some unique custom art that might look a bit like a Mox, an Underground Sea, or a Wheel of Fortune
American Grading System Americans use a different grading terminology than PSA and Cardmarket these days