Currently, the memento -- which Ohtani smacked over a left field wall during a never-before-seen performance against the Marlins back on Sept. 19 -- is a few mil away from getting to eight figures ... but Goldin says it's totally possible it reaches the plateau by the time the final gavel drops on bidding on Tuesday night.

According to the auction expert -- whose auction house is actually overseeing the sale -- most bids usually come in the final hours ... and with it already being up over $2 mil, it can threaten the $10 mil threshold for sure.

Goldin added that Ohtani's international star power -- as well as the game he had when he recorded the magical number -- could also play into the sale of it exploding this week too.

"It wouldn't blow my mind," Goldin said, "if some foreign bidder put this to eight figures and it topped $10 million."

Of course, buyers almost didn't even get the chance to drop the coin on the baseball this month -- after a lawsuit tried to halt the proceedings. But after Goldin reached an agreement with the plaintiffs in the case to move forward -- it's free game for everyone ... including Ohtani himself.

Goldin says the Dodgers superstar can bid on it like everyone else -- although he did say he and his company have not yet heard from either Ohtani or his team about potentially making an offer on it.