A 1951 Willie Mays rookie baseball card, an antique from Earth that Jake Sisko and Nog go to absurd lengths to obtain as a present for Benjamin Sisko.
The card appears in the Deep Space Nine episode In the Cards. With war against the Dominion close and the station's mood low, Jake decides to cheer up his father and spots the card among a lot of antiques to be auctioned at Quark's.
He and Nog are outbid by Dr Giger, an eccentric scientist who believes he can defeat death by keeping his cells entertained. Giger agrees to trade the card for a list of equipment, and the two boys barter favours all over the station to collect it, lifting the spirits of the crew as they go.
The trail leads them into the hands of Weyoun, who is aboard for talks with Kai Winn. Persuaded of their innocence, he lets them have the card, and Sisko is delighted.