“Alan’s a legitimate guy with legitimate stuff. He understands the card business, and he’s a great guy with a bubbly personality,” says Rose, who can’t resist a friendly barb. “Sometimes I like to tell him he’s a pain in the butt, but he’s a good pain in the butt.” Dawson agrees: “He’s got passion for the industry.”

But business is not what it once was. Rosen says that sales have declined each of the last 19 years, though he still does sales of about $2 million annually. For most of the 1980s and 1990s, Rosen attended at least 50 card shows a year; in 2012, he attended three. He talks about a recent trip to Maine that found him renting out a ballroom for three days and entertaining all of two visitors.

“I spent three days away from my phone, away from my family, away from the comfort of my own bed, to make $2,500,” he recalls. “That might sound like I’m being a pig about it, but I don’t need $2,500 at this point in my life.”

Though he remains a fan of baseball, baseball cards have long since become a commodity to him. But rather than retire, he waits — still hopeful — for the next big opportunity.

“I tried to retire a couple of years ago and, boy, sitting home all day stinks,” he says, almost cheerfully. “I guess I’ll die doing this somewhere, but there’s still the aphrodisiac of waiting for the next call.”

Rosen pauses, then adds: “You never know. The next one could be the big one.”

Larry Dobrow is a New York–based writer and a lapsed baseball-card collector. He plans to take a huge carton of his old, unearthed-from-the-basement cards over to Mr. Mint after this story publishes.