In reporting the little-known story of the Smithsonian, Sotheby’s and Sue, I was fascinated to learn that some of the people who participated in the auction still had questions about who all was in on the bidding and how exactly the Field Museum of Natural History managed to fly in under the radar to snag the world’s most spectacular Tyrannosaurus rex specimen.

David Redden, who arranged the auction for Sotheby’s, said there were 20 potential bidders that day, many of whom have never been revealed. Several people told me that they didn’t know for certain — until I confirmed it for them — that the Smithsonian’s National Museum of Natural History had a benefactor at the auction, ready to spend $2.5 million on the famous fossil.

“I don’t think I ever knew at all that the Smithsonian was there,” said Richard Gray, the Chicago art dealer who advised the Field on its auction strategy and did the museum’s bidding from a private suite, next to the Smithsonian’s.

Of course, if the Field Museum had failed to bring Sue to Chicago, the institution’s interest likely would have remained secret, too. “Had we not been successful,” said Peter Crane, then-director of the museum’s research and scientific collections, “nobody would have known that we’d ever bid on it.”

That was by design, thanks to Gray.

The art dealer and private collector, who had significant experience at high-ticket auctions, had been asked by John McCarter, then-president and chief executive of the Field, to help the museum acquire Sue.

Gray gave McCarter two pieces of early advice: Raise more money than you think you’ll need, “because the dinosaur had iconic value and there was going to be a certain kind of competition for it.”

And stop showing your hand. Play dead.

“John told me he and his colleagues had been to New York to see this dinosaur, and they’d had conversations with the auction house about it and were gung-ho about getting it,” Gray recalled. “And I said, ‘John, my advice to you is to throw Sotheby’s off track. You didn’t do the right thing by expressing so much interest and showing that you’re really going after this. It won’t serve your interests under any circumstances that they know they have you excited.’

“I made sure that they cut off all contact with the auction house. They sent only one message that they were not in the game, they weren’t players.”

Redden, the veteran Sotheby’s auctioneer, explained that it’s fairly standard for potential bidders to throw up smoke screens and feign disinterest, particularly when it comes to high-profile sales.

Sotheby’s sale 7045 on Oct. 4, 1997, certainly fit the bill; the cover of the brochure said, simply: “Tyrannosaurus rex — A Highly Important and Virtually Complete Fossil Skeleton.”

“It was very hard to know who might bid,” Redden said. “This is typical of sales of important objects. People keep their cards close to their vest; they all become very quiet. The Field Museum was a good example of that. I had fairly lengthy exchanges with them early on in the process — these fairly wonderful conversations — and then they went completely quiet. They were intentionally being as discreet as they possibly could be.”

Museum officials even denied their interest in Sue when representatives of the Smithsonian’s Natural History Museum reached out “and asked them whether they would possibly be interested in collaborating with us on some sort of purchase,” said Randall Kremer, a Smithsonian public affairs director who attended the 1997 auction on behalf of the Natural History Museum. “We came away with the understanding that they weren’t going to be bidding and weren’t interested in Sue, so when we heard the announcement that they had won, it was a surprise for me and many others.”

Among them: Redden.

“I didn’t hear a thing from them until minutes after the sale,” he said. “I was amused and totally thrilled. I had no idea the Field Museum would be bidding, and I certainly didn’t know they were working with Richard Gray, the foremost dealer in Impressionist paintings in Chicago, an important dealer who was very familiar with our auctions. Working with Richard was really quite clever.”

Field officials had asked Gray for help because, the former director Crane said, “we were a bunch of neophytes.”

As the fundraising quietly proceeded apace — led by corporate pledges from McDonald’s and Disney — Gray got in touch with Sotheby’s and asked if he could reserve a private suite for the sale. He didn’t mention who he was representing, and by then, the auction house figured the Field Museum was out. The plan was coming together, though Gray wasn’t convinced the museum had enough money in its war chest.

“We all went to New York and hung out at the Carlisle, where I have an apartment. I had a conversation with John McCarter and said, ‘I”m not completely optimistic about how we’re going to do. It’s very possible this could run away from us.’ They were were still on the job, trying to put together some other late commitments in case it was needed come auction time.”

On the day of the auction, Gray, McCarter and Crane stayed away from the Upper East Side auction house for as long as possible, to avoid being recognized. “I wanted to make sure we could keep as much of our cover as we could,” Gray said. “The people at Sotheby’s figured maybe I’d changed my mind, because I didn’t show up. But at the very last minute, we pulled up in a car. Nobody was in the lobby; everybody was already in the auction room. I got ahold of somebody and said I have a room reserved, please get us upstairs.”

They were ushered into the suite just in time for Gray to pick up the phone and make contact with Sotheby’s executive Diana D. Brooks, who was near Redden on the auction floor. The other men were instructed to look down on the floor, to see if they recognized the competition.

Bidding opened at $500,000, and Brooks, calling from the floor, kept pushing Gray to jump in, on behalf of his mystery client. Gray kept declining.

“She was doing her thing, saying, ‘Do you want to bid? Do you want to bid?’ I would say either nothing, or ‘I’ll let you know.’ I followed the action for a considerable length of time to get a sense of where this was going. My gut feeling was there was nothing to be gained from getting in early.”

Grey recalled that as bidding soared, McCarter was on the phone with Field officials in Chicago, “with the hopes that if we ran out of powder, somebody would raise their hand. There’s almost always somebody who’s excited enough in a situation like that to kick in more. And that’s what happened.”

A three-way bidding war had broken out. Gray was fighting for the fossil with the North Carolina Museum of Natural Sciences and Jay I. Kislak, a Florida real estate baron and philanthropist.

Details of the frenzied bidding are near the end of my Sunday story. Here’s the money quote from Crane, who told me that the Field Museum had reached its bidding limit:

“But Richard Gray said, ‘Let’s just do one more. That might be somebody else’s limit.'”

Sue is now on permanent display in Chicago.

As McCarter said recently: “Richard Gray knew what he was doing.”