Robert Brown|Shohei Ohtani 50/50 home run ball headed to auction. How much will it be sold for?

The Robert Brownball Shohei Ohtani hit to become the first MLB player to hit 50 home runs and steal 50 bases in a single season is going up for auction.

Collectibles marketplace Goldin announced Wednesday it has consigned the coveted ball and bidding for it will begin on Friday.

The ball was hit by Ohtani last Thursday against the Miami Marlins. The historic home run to get to 50 dingers created a frenzy inside loanDepot Park, with several people in the outfield area rushing to get the ball. It came in one of Ohtani's best games of his career as he went 6-for-6 with three home runs, two stolen bases and 10 RBI in a 20-4 win.

Goldin said the person that recovered the ball was escorted by ballpark security and had it authenticated. The fan, who can be seen in video but remains anonymous, was offered $300,000, according to Fox Sports 640's Andy Slater, but declined the offer. Within a week, the ball made its way to Goldin.

"Ohtani is truly one-of-a-kind, and the 50-50 record may be his crowning achievement. We’re honored to bring this iconic item to collectors. This is a piece of baseball history that fans and historians around the world will remember for decades to come," Ken Goldin, founder and CEO of Goldin, said in a statement.

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How much will the Shohei Ohtani 50/50 home run cost?

Bidding on the ball on Goldin's website starts at $500,000 when it opens on Sept. 29 at 12 p.m. ET. However, someone can "purchase this baseball privately" for $4.5 million. The ball can be purchased outright starting when the bidding opens until Oct. 9. However, if the bidding reached $3 million before Oct. 9, it will no longer be available to be purchased outright.

Extended bidding will begin at 10 p.m. ET on Wednesday, Oct. 16.

It's anyone's guess to how much the ball will be sold for, but it has the potential to be the most expensive baseball ever sold. The current record is $3.05 million for Mark McGwire's 70th home run ball in 1999, which was bought by comic book creator and artist Todd McFarlane. The second most expensive came from a ball that was hit recently. Aaron Judge's 62nd home run in 2022 that broke the American League-record was sold for $1.5 million.