Jackie Flat Gets $32 M.

At 1040 Fifth Avenue, the former home of Jacqueline Kennedy Onassis is about to change hands.

Hedge-fund manager Glenn Dubin has recently signed a contract to buy the $32 million apartment from billionaire David Koch, according to a source familiar with the deal.

Mr. Dubin—who currently resides at nearby 1010 Fifth—is managing partner and co-founder of Highbridge Capital Management. But more interestingly, he’s also chairman of the Robin Hood Foundation, a favored charity of the late John F. Kennedy Jr., who also had a seat on its board and who grew up in the apartment Mr. Dubin is buying.

Through a spokesperson, Mr. Dubin declined to comment. And though Mr. Koch, the seller, would not identify Mr. Dubin as the buyer, he was happy to talk about the apartment he’s leaving behind.

When Mr. Koch bought the apartment back in 1995, he said, it had to be completely refurbished.

“Mrs. Onassis was very conservative financially, and she didn’t spend much on it,” said Mr. Koch. “We gutted the apartment and redid everything.”

At approximately 5,300 square feet, the 15th-floor spread includes five bedrooms and five and a half baths. There is also a library, a conservatory, a dining room, two terraces and three fireplaces.

But for the billionaire Mr. Koch—whose third child was born a week ago—that wasn’t enough space for him, his wife, three children, his mother-in-law and three nannies.

“As much as I love the old Jackie Onassis apartment, it wasn’t large enough,” said Mr. Koch.

Considering that Mr. Koch is worth an estimated $12 billion, it’s not surprising that he will be heading over to the much-celebrated 740 Park Avenue, home to fellow billionaires like Steve Schwarzman and Ronald Lauder. Purchased for $18 million two years ago, Mr. Koch’s new duplex has about twice as much space.

And he’s just completed another big renovation. Previously owned by the Japanese government, the new place hadn’t been touched in about 50 years, he said.

“Obviously, after all the money we paid for the apartment, we wanted to make sure it was first-class,” said Mr. Koch, who worked on the two-year gut renovation with renowned architect Peter Marino.

Although Mr. Koch just officially moved into 740 Park a few weeks ago, he’d already learned quite a bit about the building’s history from author Michael Gross’ biography of the storied co-op. And unlike some snooty 740 Park residents, Mr. Koch was more than happy to attend the book party: “[Mr. Gross] told me that I was the only occupant that came to cheer him on.”

So if the deal goes through, Mr. Koch—who paid $9.5 million for the Fifth Avenue apartment—could make a hefty profit (not that he really needs it).

Mr. Koch said that about 30 potential buyers passed through the apartment before they found a match. Now the couple purchasing the apartment—we say the Dubins; he won’t say anything—go before the board within the month, according to Mr. Koch.

Leighton Candler, of the Corcoran Group, has the listing. Ms. Candler confirmed that the apartment is under contract, but also would not confirm the identity of the buyer.