More than 25 years after the infamous theft of masterworks from the Isabella Stewart Gardner Museum in Boston—and with not a single of the 13 stolen works recovered to date—the museum’s board of trustees announced yesterday (May 23) that it is doubling the size of the reward for information leading to return of the works, to $10 million. The last time the reward was increased, from $1 million to $5 million, was two decades ago, in 1997.

The Gardner Museum.

The increase coincides with yet another false start as a Virginia con man, Todd Andrew Desper, was recently arrested for fraudulently “offering” for sale Vermeer’s The Concert, for $50 million online. Desper used Craigslist, encrypted email, and the alias, “Mordokwan,” to post the announcement according to a criminal complaint filed in US District Court in Massachusetts.

Gardner museum security director Anthony Amore told artnet News that there is no connection between the fraudulent sale attempt and the reward increase, which came “as a result of a vote at a prescheduled annual board meeting.” Tipsters who spotted the work for sale online informed the museum about it.

“Typically stolen masterpieces are either recovered soon after a theft or a generation later,” said Amore. He added that the offer is a sign that “the investigation remains active” and that the museum is optimistic the works can still be recovered.

The Gardner Museum robbery remains the largest in art history. As has been documented, in the early morning hours of March 18 1990, two thieves disguised as police officers gained access to the museum and made off with more than $500 million worth of artwork, including the aforementioned Vermeer painting, The Concert, Rembrandt’s Christ in the Storm on the Sea of Galilee (the only known seascape by the artist) and A Lady and Gentleman in Black, Edouard Manet’s Chez Tortoni, and Edgar Degas’ Leaving the Paddock.

“It is our fervent hope that by increasing the reward, our resolve is clear that we want the safe return of the works to their rightful place and back in public view,” said museum board president Steve Kidder in a statement. The offer is set to expire on December 31, 2017.

Meanwhile, according to the criminal complaint, dated May 19, in January of this year, the FBI received a tip that The Concert was being offered for $50 million on Craigslist by a seller who instructed potential buyers to create a ProtonMail, encrypted account and communicate with an email address listed as “[email protected].”

Desper later told federal agents that “mordokwan” is a form of martial arts that he had studied for several years.

A similar listing on Craigslist in London, also connected to Mordokwan, which the museum was also tipped off about, offered the Rembrandt seascape for sale for $5 million.

Amore set up a ProtonMail account to communicate with the buyer. The criminal complaint includes email exhibits of their correspondence that read like the type of bank account letter scams that show up unsolicited in email offering millions of dollars in unclaimed funds in exchange for advance fees and account information.

Amore claimed to be representing an interested buyer in Florida, who he described as an “ex-Russian politician” who had previously sent him overseas twice—to London and Berlin—in unsuccessful pursuit of Vermeers.

Desper, aka Mordokwan, thanked the sender, telling him it was “a pleasant surprise to receive one email, out of many, from someone who actually took the time to read what I said.”

Desper attached a photo of what he said was a “close-up pic of the arm of the woman playing the piano,” adding “please understand, for several obvious reasons, I do not, nor will I ever meet.” Helpfully, however, he offered to ship the “VerMeer” from an undisclosed location to any location in the world. He wrote that he would conceal the painting behind another before shipping.

A Gardner Museum conservator concluded that the section of the painting pictured was not from The Concert. According to the complaint: “While the FBI had significant doubts that Mordokwan possessed or had access to The Storm or The Concert, given the means he was using to offer them for sale, the importance of these artworks, and the longstanding investigation we decided to thoroughly pursue this lead.”

Further, if he didn’t have the paintings, “it appeared that he was engaged in a multi-million dollar scheme to defraud, targeting foreign buyers.”

During the course of the investigation, the FBI also learned that Desper was offering the works online to buyers in Egypt and London. The FBI tracked the fraudster down using an address that in Virginia that turned out to be a business he owned as well as a PO box at a local UPS store. He had instructed Amore to send a $5 million cashier’s check to the address, telling him in separate emails “Painting is real,” and, in response to his question about whether the work was “Real from the Gardner Museum?” he responded: “The one and only.”

Desper has been charged with wire fraud and attempted wire fraud.