Goldin revealed on Wednesday afternoon it'll oversee the sale ... after the man who caught it earlier this month at the Dodgers vs. Marlins tilt in Miami reached out to the auction experts directly.

The company said in a statement that while the get-in price for the ball is half a mil ... fans can purchase it outright for a staggering $4.5 million.

"If bidding reaches $3,000,000 prior to October 9 however," Goldin officials wrote, "the option to purchase privately will no longer be available, and interested parties must compete and bid for the baseball."

It's a whopping sum ... although it's hard to imagine it not being worth it.

After all, it marked the first time in MLB history that a player had reached the 50 home run, 50 stolen base plateau. It's also got some markings on it that make it really unique.

Check it out -- there's black scuffing on the surface that appears to be from Ohtani's bat. There's also numbers "4" and "3" written in pencil on it. Plus, there's an MLB Authenticated Hologram -- proving baseball officials have dubbed it the real deal.

Artifact seekers can officially begin placing their bids on the memento on Friday. Bidding will close later next month.