The rare “Jumbo” T206 Honus Wagner card will go up for sale in September, Yahoo Finance has learned. It’s a tiny baseball card from 1909, and it has a good shot at selling for more than $4.4 million.

For the uninitiated: Honus Wagner cards from the American Tobacco Company’s T206 series are the most valuable baseball cards in the hobby. Not all cards from that series, which included 524 cards, are as valuable, though Ty Cobb cards from the series also sell for astronomical figures. Wagner’s card is special because Wagner demanded he be removed from the series, either because he didn’t like the cigarette company marketing to children or because he wanted money from the company to use his image.

As a result, there were only about 200 Wagner cards made, there are only 50 or so in circulation today, and most are in terrible shape, so the best-graded cards have switched hands many times and risen steadily in value.

This particular Wagner card has a rating of 5 on the 10-point PSA scale that grades the condition of baseball cards. Because of the scarcity of the cards, a 5 is very high; there are only three known grade-5 Wagner cards. The “Jumbo” is either the best or second-best T206 Wagner card out there, depending on whom you ask.

But it is also imperfect, and ironically, this boosts its value. The card is called “jumbo” because of a cutting error: it has a larger border, one-sixteenth of an inch larger all around than the others. At the time of manufacturing, cutting was done by hand on one big sheet; this card was not cut to the right size. (You can even notice, just barely, at the bottom right, the beginning of the next card from the sheet.) The cutting error is why the card is labeled PSA 5 (MC), for “miscut.”

The card last sold in 2013 for $2.1 million, to a buyer who chose to remain anonymous. Ken Goldin, founder of Goldin Auctions in New Jersey, which handled that sale and has sold $600 million worth of memorabilia, says the buyer was a “private businessman” who did not plan to re-sell the card so quickly, and had intended to hand it down to his children. But the market has exploded to such eye-popping heights that the buyer is ready to make some money—perhaps even to double his investment.

Front and back of the 1909 T206 PSA 5 (MC) Honus Wagner card More

The current record-holder for the highest price fetched at public auction by a piece of sports memorabilia was not a card, but a jersey: Babe Ruth’s game-worn jersey from 1920 that sold for $4.4 million in 2012.

Why could the T206 Jumbo Wagner go for higher? It’s older (by 11 years), more coveted (cards typically fetch more money than game-worn jerseys or game-used gear), and no other high-grade T206 Wagner card has gone up for public sale in 15 years, apart from this one in 2013.

But it’s really about the market explosion of the last few years. “We have seen a seismic shift,” Goldin says, “a tremendous influx of new collectors with high disposable income.” To name just one example: A 1968 Topps rookie card of the pitcher Nolan Ryan sold this year for $80,000. And that’s a player who’s not even dead.

Goldin theorizes that the latest venture capital flood in tech has helped the boom. “It’s a purely male-dominated hobby, and you’ve got a combination of tech-money people and hedge-fund people—they love sports but they’re not going to buy a baseball team. This is something they can afford and enjoy.”

Before the Babe Ruth jersey sold in 2012, a different T206 Wagner card set the sports memorabilia record in 2007 when it sold for $2.8 million, through private sale, to Arizona Diamondbacks owner Ken Kendrick, who still owns it today. That one is commonly called the “Gretzky” T206 Wagner because it was once owned by hockey great Wayne Gretzky. An ESPN “30 For 30” short film called the Gretzky T206 Wagner “the holy grail.”

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