Fishlegs' Dragon Cards

Fishlegs' Dragon Cards are like the Dragon Eye Lenses, as they tell him and his friends about the "new" unknown dragons they've come across; he keeps them in a pouch on his belt. They each have an image of a dragon, along with their class, size, speed, abilities, strengths and other important information. They were first introduced in the second film.

Dragons: Race to the Edge, Season 3
In "Crash Course", when the Riders came across the Cavern Crasher on Fireworm Island, Fishlegs got the cards out of the pouch to identify the dragon. Fishlegs claimed that he had been working on them for months, before telling his friends about it. The Cavern Crasher Card gave them an idea why it was attacking the Fireworm Queen's nest, as well as the dragon's abilities, class and speed.

Dragons: Race to the Edge, Season 5
While the Dragon Riders were following Great Protector to Vanaheim in "A Matter of Perspective", Fishlegs looked through his Dragon Cards to find out the speed of the Eruptodon.

The Dragon Cards made a appearance in "No Dragon Left Behind ", where Fishlegs was trying to search for a cure on Slitherwing venom.

How to Train Your Dragon 2
After Eret brought Astrid and the other Riders to Drago's location, they saw a group of ships around a "pool" of bubbling water. Fishlegs got his cards out to see if those bubbles were made by dragon and what kind it would be, but he had trouble finding the card that can tell him what dragon it is. When Drago's men "found" them, Fishlegs dropped the cards when he flung his hands up in surrender. It's most likely that he came back for the cards or picked them up.

The Serpent's Heir
On the way to Nepenthe, Fishlegs tried to identify a mysterious deep sea dragon he saw, by looking through the Dragon Cards.

Trivia

 * The cards and the pouch they're kept in appears in the game Dragons: Rise of Berk as a collectable in completing collections.
 * It's possible that Fishlegs had worked on them after the Dragon Eye had been taken by the Dragon Hunters, and that some of the cards' information is from some of his Dragon Eye notes as well as Bork's Papers and the Dragon Manual.