A baseball card was a type of collectible card popular on Earth in the 20th and early 21st centuries, on which was printed the likenesses and statistical information on professional baseball players.
Kivas Fajo possessed a mint condition Roger Maris baseball card, and had preserved the scent of the chewing gum it had originally been package with. (TNG episode: "The Most Toys")
Benjamin Sisko kept a Buck Bokai baseball card on his office desk on Deep Space 9. (DS9 episode: "If Wishes Were Horses")
In 2375, Jake Sisko and Nog went to great efforts to obtain a Willie Mays baseball card for Captain Sisko. (DS9 episode: "In the Cards")