Waterville bookstore owner Robert Sezak doesn’t collect stamps, but his search for a rare, reissued upright Jenny was different.

Sezak regularly buys large-denomination stamps so he can ship online orders from his downtown bookstore. When he heard about the upright Jennies, he made it a point to try to get his hands on some.

The regular red and blue stamps, which commemorate what is probably the most famous stamp printing error by the U.S. Postal Service, have an image of an upside down, or inverted, biplane. The rare special stamps show the plane right-side up. That “upright” or “corrected” Jenny is the difference between a $12 sheet of $2 stamps and a collector’s item worth thousands of dollars.

“I was looking for them. I knew they were out there,” Sezak said. “I figured, since I used the stamps anyway, I could casually seek them out.”

Two years ago, shortly after releasing a set of stamps in honor of the famous inverted Jenny mistake originally issued in 1918, the U.S. Postal Service revealed it had concealed 100 limited edition six-stamp sheets among the 2.2 million of the stamps released to the public. Since the stamps were introduced in 2013, less than a quarter of the rare version have been found.

Sezak bought the 24th limited edition sheet at the Waterville post office in mid-September.

It is now being held under lock and key at James D. Julia Inc., an auction house in Fairfield. It will go up for auction Feb. 3-5, and is listed for $40,000 to $60,000.

“I don’t collect stamps. I just thought it would be an interesting endeavor,” said Sezak, who is also chairman of the Fairfield Town Council.

The commemorative stamps come individually wrapped in a sealed envelope so customers can’t see if they are buying the special edition. The intent was “to re-create the excitement of finding an inverted Jenny when opening the envelope and to avoid the possibility of discovering a corrected Jenny prior to purchase,” the Postal Service said in a news release. A congratulatory note comes with the special stamps, directing customers who find them to contact the Postal Service for a certificate of authenticity signed by the postmaster general.

Tony Griest, an assistant department head for fine art at James D. Julia Inc., said the auction house doesn’t normally feature stamps and didn’t know about the upright Jenny until Sezak approached them.

“It intrigued us from the standpoint of its rarity,” Griest said.

The set of six stamps for auction includes the congratulatory note found with the stamps and the certificate of authenticity.

But the upright Jenny promotion has sparked criticism, including from the Postal Service Office of Inspector General, the service’s watchdog agency.

In a management alert issued July 15, John Cihota, the deputy assistant inspector general, found that the Postal Service “strongly and inappropriately influenced the secondary market by creating the rarity,” adding that two sets of upright Jennies had sold for $51,750 and $55,000, respectively.

In his memo, Cihota found that the Postal Service hadn’t cleared the promotion with its legal department and confusion with its distribution plan meant that only one sheet of upright Jennies was sent out between March and December 2014. When staff discovered the mistake, they randomly selected three customers who ordered the stamps and sent them an additional sheet of upright Jennies in violation of Postal Service policy.

Meanwhile, 23 of the stamp sheets still have not been distributed.

The original Jennies were issued in 1918. It was the postal service’s first 24-cent airmail stamp, a red and blue design featuring the image of a Curtiss JN-4H biplane, otherwise known as the Jenny. In a rush to celebrate the first airmail flight with the stamp, 2.2 million of the stamps were printed with a sheet of 100 stamps printed incorrectly with the aircraft upside down making it into general circulation.

That sheet of Inverted Jennies was bought by a 29-year-old cashier from Washington, D.C., named William T. Robey shortly after the airmail stamp was released. Robey flipped his purchase to a Philadelphia stamp dealer a week later for $15,000, according to the postal service.

Since then, the Inverted Jenny has become one of the most sought-after stamps in U.S. history. In 2007, a single original Inverted Jenny sold for $825,000 at Heritage Auction Galleries in Dallas, Texas, and in 2005 a block of four stamps was valued at $2.97 million, according to the Robert Siegal Auction Galleries in New York City.