Confession: I was once a huge fan of Pokémon cards. I’d host neighborhood tournaments in my backyard and throw the most unnecessary temper tantrums if a store sold out of their heinously overpriced supply. To excuse my reckless spending on the cultural fad, I’d tell my parents, who tracked my finances that were mostly found in birthday cards, that these playthings would be worth big money some day.

According to a new comprehensive guide on Pokémon cards from website Mashable, I was correct. Well, partly. These cards can be worth some major coin, but in order to reap rewards, your adolescent efforts must have reflected those of a true Pokémon Master.

First, let’s take care of the obvious. There are two main factors that determine the value of every Pokémon card. The first is rarity, or the number of copies in existence. The second is quality, or the card’s physical condition. With these two guidelines established, let’s take a gander at which cards in your collection could be worth thousands.

Coined the “crown jewel” of Pokémon cards, this beauty is the rarest of all, as it was never actually in circulation. The 39 copies that exist were solely distributed as prizes at three different Pokémon illustration contests held in the late 1990s. The card, which displays an image of Pikachu wielding a painting brush, recently sold for $55,000 at an auction.

Mistakes are money. Back in its heyday, some Pokémon cards were released with tiny imperfections, like a misplaced holographic or a misspelling. These minor errors can increase the card’s value tenfold. A standard card with the slightest of imperfections could be worth anywhere from $100 to $500.

Everybody who has ever expressed even the slightest interest in Pokémon knows the Charizard card is the rarest of the bunch. But according to Mashable, a first-generation “shadowless” Charizard card can retail for $3,000, whereas your standard Charizard would sell for a measly $10.
The “shadowless” moniker references the border around the Pokemon’s portrait, which typically have a drop shadow on the right and bottom sides, except for the very first cards ever produced. This wasn’t an error but a design choice that was changed early in production. Because of the change, shadowless cards are worth way more than those produced afterward. For example: A shadowless Blastoise and Venusaur are worth just under $1,000; they’re otherwise worth $20. Even common and uncommon shadowless cards retail for $50, provided they’re in good condition.

If you aren’t one of the 39 people to yield an “Illustrator” card, don’t despair. Even regular old Pokémon cards can fetch you some cash—if they’re in good shape. Your run-of-the-mill Pokémon cards can still sell for $1 to $5, which, if you have hundreds like I do, could amount to a sizeable payday. However, some popular holographic cards, like Blastoise or Zapdos, could earn $20. For context: That’s about the same price as the rarest of Beanie Babies. Meaning yes, those bean-filled plushies are still worthless.