When Aeder was in his 30s, he said, he decided to sell his entire collection at a card show. That plan did not work out.

“Instead of selling, I wound up spending every penny on me buying new cards,” he said.

After completing the sets from his childhood, he turned to collecting the cards of Jewish baseball players.

“Many collectors are happy just to get one card of each player,” said Martin Abramowitz of Newton, Mass., whose collection ended up with Aeder after Abramowitz sold it to someone else to help pay for his daughter’s wedding. “Jeff is determined to get every card of every Jewish player.”

Aeder sees curating such artifacts as an extension of the philanthropy that prompted Chicago Magazine to pick him and his wife, Jennifer Levine, as its “Chicagoans of the Year” in 2013. Among other things, the couple founded the Wolcott School for children with learning disabilities and Milt’s Barbecue for the Perplexed, a kosher restaurant that donates all of its profits to charity.

In March, Aeder introduced the online Jewish Baseball Museum. “My idea was to celebrate both the rich history of Jews in America and how baseball was an opportunity to fit in,” he said. “And today, now that they fit in, it’s an opportunity for them to feel more Jewish.”

McKee said he had no idea that Zinn was Jewish when he bought his card more than 20 years ago. McKee valued it for another reason. It was part of one of three sets that appeared as an insert in The Baltimore News and that provided a full season schedule on the back of each card.

A 1914 version of these so-called schedule-backs included the first card ever made of Zinn, who was then in his fourth season and playing for the Baltimore Terrapins of the Federal League.