Fortunately for the seller, a late flurry of action Sunday night brought a winning bid of more than $3.2 million — more in line with his expectations.

The highest price ever paid at auction for a comic book had been $2,161,100, when another high-quality copy of Action Comics No. 1 — widely rumored to have been stolen from actor Nicolas Cage before being recovered — was purchased by an anonymous buyer in 2011.

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Yet the owner of the book on the block this weekend, Darren Adams — a collector who runs the Pristine Comics shop in Washington state — says that he paid seven figures for his issue several years ago, and that he turned down multimillion-dollar offers for the book prior to going to auction.

“The idea of sitting at $2-million was never really a risk in my mind,” the collector tells The Post’s Comic Riffs. “Too many people have such an interest in this book.”

Adams said before the auction’s close that he would like to see his book sell for a figure north of $3 million. He got his wish.

The winning bid, according to eBay: $3,207,852.

“This book is like a museum piece,” he tells Comic Riffs. “It’s a freak-of-nature work.”

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Only several dozen unrestored copies of Action Comics No. 1 are known to still exist, Adams says, and perhaps only seven of them are in such good condition that they receive a grade higher than “6.0” from the Certified Guaranty Company. (The independent CGC grades comics on a scale of 1 to 10.)

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Adams’s Superman book is graded at “9.0,” an almost unheard-of condition for this issue, which hit newsstands in the summer of 1938. And among the known copies, Adams tells Comic Riffs, “only two have perfect-white pages” — including his.

All because in terms of ideal storage conditions, the book’s provenance seems almost as if by providence.

2.

A COMIC BOOK IS best stored in a place that’s “cool, dry and dark,” Adams says, with low exposure to oxygen. His Superman book was purchased off the newsstand in the ’30s by a man who kept it in a cedar chest at high altitude in the mountains of West Virginia, where it rested for decades until that owner himself was laid to rest.

“What happens next is kind of cool,” Adams tells The Post. “This young guy — a collector who’s getting going — goes to the estate … and sees this book and sees the pages are incredible. So he [bought it and] reconstructed himself a similar cedar chest” to store it in.

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Adams, 53, began as a young collector himself. He was an avid comics reader by age 12, pulled in by artist Neal Adams’s early-’70s work on Batman.

As a “military brat,” Darren Adams says, he moved a lot, going to 13 different schools, in the Seattle area, and Oregon, and Germany. He was always “the new kid,” and had no siblings, so comic books often kept him company. By age 11, he started a lawn-mowing business — renting push mowers and getting friends to do the mowing for a cut of the money — and poured much of his profits into buying comic books. Like some latter-day Tom Sawyer, “I was already a wheeler-and-dealer,” he says.

Eventually, Adams became largely a collector and dealer of sports trading cards — an area of the business in which he could be sufficiently dispassionate — as opposed to his beloved comics.

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“I had no emotional attachment to trading cards,” Adams says of entering the business in his early 20s. “And I applied everything I learned with comic books.”

About a decade ago, though, the books again beckoned, and Adams began collecting comics as a sideline business. More than 30 years after first cracking a Neal Adams Bat-book, his cartoon fandom and sense of commerce met.

3.

FOR YEARS, ADAMS has been willing to travel around the world to buy collectibles. Because of all his experience, he didn’t get his hopes up when a seller within the continental United States contacted him several years ago to offer a 1938 Superman book.

“I saw this scan — a private e-mail with an image — and held some reservations,” Adams recalls. “Any marking on a book at all can impact the value of a book by hundreds of thousands of dollars.”

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But then he hopped on a plane and saw the book — this rarest of Action Comics No. 1 — in person. “The cover was so bright and vivid,” Adams tells Comic Riffs. “The corners were real sharp. I was very surprised.

“Then I saw the interior of the book, and I was blown away by the depthness of the color and the suppleness of the page.”

Adams had treasured touching an Action Comics No. 1 on a prior occasion — and it’s CGC grade had only been a “6.5.”

“I saw one at [San Diego] Comic-Con,” Adams tells me this week. The online auction house Metropolis had the issue at its booth. Metropolis co-owner Vincent Zurzolo let Adams, the veteran collector, hold the book. “Then my son holds it,” Adams recalls, “and I say to him: ‘Remember this. You’re holding a “6.” ‘ That’s how special it felt.”

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Adams compares that experience with encountering his own special Superman book. “Fast-forward to this moment in time,” he says. “I’m looking at this book — this might be the best copy in existence.

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“It was a surreal moment.”

Adams paid a seven-figure sum, he says. The potential “best copy in existence” was his.

A few years later, in a twist of fate and interest, Zurzolo would come back into the picture when Adams’s copy went on sale.

4.

SOME COMICS FANS WOULD never sell a book this rare. But Adams is a collectibles businessman, too, and keeping valuable books in circulation, and making a profit in return, is what he does.

“I actually held it for a few years — I was so excited about this book,” the collector from Federal Way, Wash., says. “And equally exciting to having a book of this condition is the fact that nobody knew it existed. Most books have a history … but this book was totally off the grid, and nobody knew about it till I made it known.”

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Once Adams decided to sell, his next step was to decide how he wanted to sell it. Metropolis/ComicsConnect and Heritage Auctions have handled record-breaking vintage comic books. Yet Adams believed eBay could deliver a wider general audience.

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“I’ve done business with the major auction houses,” Adams says, but “I didn’t want to simply stick with the comics crowd [of buyers]. I wanted to get a worldwide audience for this book. … And nobody has a bigger reach than eBay.”

“Darren was sort of exploring his options and trying to figure out the best avenue for selling what is obviously an extraordinarily special book,” Gene Cook, eBay’s general manager of emerging verticals, tells The Post’s Comic Riffs. “In talking to us, he wanted to gauge our level of excitement and interest.

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“We love everything about this book,” Cook continues. “We love the pop-culture aspect of it … and the level of its quality is truly unprecedented. The people who have held it in their hands — it’s a magical experience.”

Cook also notes eBay’s audience, emphasizing that the California-based company has 149 million active buyers around the world. Adams had said he wanted to make sure this book’s sale was widely known in prime foreign markets.

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And the way this book was first found, Cook says, in “a dry, cool environment with little oxygen, stacked with other comic books for stunned people to rediscover it, was like going back in time.”

(Cleveland teenagers Jerry Siegel and Joe Shuster, of course, co-created Superman in the ’30s, partly inspired by adventure comic strips of the day. They would sell the rights to Superman for just $130 — as part of a $412 check — to Detective [DC] Comics.)

The Adams/eBay teaming comes with another Superman wrinkle. The collector wanted to give some portion of the sale to charity. In talks with eBay, they decided the charity of choice would be the Christopher & Dana Reeve Foundation for spinal-cord injury and paralysis research. (According to the foundation, the donation will be 1-percent of the sales price.)

Christopher Reeve died in 2004, nearly a decade after an equestrian accident in Virginia left him a quadriplegic. In the ’70s, of course, the strapping, 6-foot-4 Reeve became a household name when he began starring in Richard Donner’s Superman films.

“Christopher Reeve is the most iconic Superman of them all … ,” Adams says. “And it’s a great cause — stem-cell research. I can’t think of a more natural charity to align with this book.”

5.

DARREN ADAMS HEARS the doubters. He knows that some people criticize placing a high price tag on a comic book.

“The mind-set is different than it should be,” Adams says. “The first time this comic book cracked a million [at auction in 2010], I thought it was dirt-cheap. It is the holy grail.”

Zurzolo and his fellow New York comics dealer, Stephen Fishler, certainly feel the same way. They said Monday that they were the ones who submitted Sunday’s $3.2 million winning bid for the book.

To those people who question why this book should sell for, say, $3-million, Adams’s retort is: “Why shouldn’t it?”

At least since an industry dawned with his Superman book, Adams knows, comic books have generally been perceived in the United States as a “low” art built on rapid publication and mass sales once routinely in the millions. Compare with that with Europe, a continent of comics sophistication, where original Tintin art signed by the creator, Herge, sold this year in Paris for $3.1 million — the previous auction record for a comics work.

Besides, Adams asks, how is this so different from stamp collection?

Just two months ago, he notes, a rare 19th-century stamp sold in New York for a record $9.5 million: “And it was a one-cent postage stamp.” (In 1938, for the record, the cover cost for a Superman comic book was 10 cents.)

Whether it’s a Ming vase or a comic book, rare art is rare art, says Adams, re-emphasizing that his book is “a museum piece.”

Then there is high-priced art that has a related origin story. Two years ago, a 1964 Pop Art work sold at Sotheby’s in New York for $44.9 million — a then-record for a Roy Lichtenstein painting.

The title of the work was “Sleeping Girl” — an oil and Magna on canvas painting that vividly “pops” in yellow and red in between flesh-toned Benday dots. And the visual source that Lichenstein’s great work was so heavily based on?

A single panel from the 1964 comic book Girls’ Romances, No. 105.

And the imprint behind that book?

DC Comics — the same publisher that produced Adams’s 1938 Superman.

As Lichtenstein once noted while speaking to the National Cartoonists Society, he was starving in his studio — broke — when he literally drew inspiration from a source that ignited his career as a Pop superstar.

All he had to do was turn to comic books to yield millions.