On a bright May afternoon in 2007, a German artist and printmaker named Hans-Jürgen Kuhl took a seat at an outdoor café directly opposite the colossal facade of the Cologne Cathedral. He ordered an espresso and a slice of plum cake, lit a Lucky Strike, and watched for the buyer. She was due any minute. Kuhl, a lanky 65-year-old, had to remind himself that he was in no rush. He'd sold plenty of artwork over the years, but this batch was altogether different. He needed to be patient.

Tourists milled about the platz in front of the cathedral, Germany's most visited landmark, craning their necks to snap pictures of the impossibly intricate spires jutting toward the heavens. Kuhl knew those spires well. He had grown up in Cologne and painted the majestic cathedral countless times.

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On the other side of a low brick wall surrounding the café, Kuhl finally spotted her. Tall, blond, and trim, Susann Falkenthal looked about 30. As was the case during their previous meetings, she wore practical shoes, an unremarkable blouse and pair of pants, and little makeup. Kuhl thought her plain look was something of a contradiction for a businesswoman who drove a black BMW convertible, but no matter.

When they first met a few months earlier, Falkenthal said she was an events manager from Vilnius, Lithuania, and gave Kuhl a card printed with a Vilnius address as well as an address from the German city of Essen. Her German was flawless.

This appointment by the cathedral was perhaps their 10th, and they greeted each other with a kiss on each cheek. Over the past few months, they had been meeting at Kuhl's studio. She brought cake; he made coffee. They discussed jazz, Kuhl's years as a fashion designer, the time Kuhl had met Andy Warhol, vacation spots on the Spanish island of Majorca, and eventually counterfeit US dollars.

>If Kuhl couldn't sell his beautiful fake bills, they would just end up rotting in a storage locker.

Early on, Falkenthal said she did a lot of business with Russian contacts in Vilnius, where unscrupulous types would sometimes try to bribe bouncers with fake $100 bills to gain access to exclusive events organized by her firm. Kuhl sympathized and mentioned a couple of tricks for detecting forgeries. "It's easy to see and feel if it's fake or not," he told her.

A few weeks later, Falkenthal told Kuhl that she had a high-end party coming up in August. Would he be interested in printing the tickets for it? She wanted them to have unique serial numbers and some way to protect against forgeries. Kuhl suggested a strip that shines brightly when exposed to an ultraviolet lamp. Falkenthal told him the official order was for 300 tickets but then with a wink requested he print an extra 50 for her to sell on the side. She obviously isn't the Pope, Kuhl thought. Working with her might get interesting.

After Kuhl printed the tickets for Falkenthal—including the extra 50—and was paid, he decided to take his chances with her. Not in the romantic sense, although during some of Falkenthal's visits to his studio, Kuhl certainly noticed the way she'd drape an arm on the back of his desk chair and lean over him to inspect print drafts on his monitor. He thought they could do business. There were risks, Kuhl knew, but he tended to trust people. So he showed her a counterfeit $100 bill that he had made. As a precaution, he told her the sample had come from someone in Poland. There may be many more, he added. She asked if she could borrow it to show to a Russian friend. He said sure but warned her to be cautious. He knew from experience that this "area of business" was full of informants and undercover cops.

Falkenthal called Kuhl two weeks later. Her contact was impressed with the sample and interested in a purchase. They started with a test batch of $250,000, which she bought for 21,600 euros. The price was typical for forgeries, which generally sell at a steep discount because so much of the risk is borne by the buyer. As a consequence, counterfeiting is profitable only on a large scale. During that exchange, Kuhl told Falkenthal that he and his business partner had about $8 million more in currency to sell. "If the contact is satisfied with this first installment, we should talk," he said. Ten days later she got back to him with good news: The man was "happy with the forgeries" and wanted to make a larger purchase. How about $6.5 million?

Seated at the café across from the cathedral that afternoon, Kuhl handed Falkenthal a note with a price for this new order: 533,000 euros for the $6.5 million in counterfeits. She agreed. Then they decided to make the handoff the next day at his studio. Kuhl also told Falkenthal that to ensure his safety he would have someone nearby during the exchange, just to be sure the handover went smoothly. "I have no choice," he said, "even though I basically trust you."

When Kuhl and Falkenthal stood up to part ways, Falkenthal added that she would bring her own boxes. After all, $6.5 million in $100 bills weighs about 150 pounds.

5// Make the Plates From his computer, Kuhl printed the grids onto film—basically transparent paper. Then, one sheet at a time, he placed that film atop specially treated lithographic plates made of aluminum. In a darkroom, he fired ultraviolet light at each plate. Light passes through the film where it's clear but not where there's ink. The result after processing, much like with photographic film, is a reverse of the desired image. 7// Fake the UV Security Strip Authentic Benjamins feature a vertical strip of material that shines red when exposed to ultraviolet light. Kuhl made an additional offset plate to print this element. He used it to apply not a color but an invisible UV-sensitive ink that would appear dull red when viewed under a UV lamp. "I printed what I couldn't see," he says, recalling the trial and error required to determine just the right amount of ink to apply. Illustration: James Yamasaki 8// Simulate the Texture of Real Cash Certain areas of US currency have a raised texture. To print the scratchy color-shifting "100," Kuhl mixed green glitter with color-shifting pigment and applied it using a silk-screen press. To prevent this second coating of ink from slumping and blurring, he also applied a UV-sensitive clear lacquer, which dries instantly when exposed to ultraviolet light. Illustration: James Yamasaki 6// Print the Bills Kuhl could now clip the plates into his Heidelberg GTO 52 offset printer and run his paper through the machine. The plates are mounted on spinning cylinders and, as they spin, are coated with the appropriate color ink. The image is then transferred from the plate onto the paper, laying down each layer in succession and creating sheets of almost-complete $100s. Illustration: James Yamasaki 4// Create Digital Files for Each Printing Layer Kuhl duplicated each file image 12 times and laid them out in a three-by-four grid for printing, giving him a sheet of 12 partially completed notes. He did the same for each of the four layers. With these files he was now ready to commence the offset printing process, which involves applying successive layers of color and imagery. 3// Deploy Photoshop He used photo-manipulation software to clean up a hi-res scan of a $100 bill, removing certain details like the serial number and the forest-green Treasury seal on the front of the note. He made another image of only the black components on the front of the bill and yet another of the artwork on the back. He also prepared sheets consisting of only bogus serial numbers—about 500 of them in total. Illustration: James Yamasaki 2// Mimic Security Features Kuhl used silk screen to apply features that, on a real bill, are visible only when the note is held up to the light. He created a convincing watermark to the right of the Ben Franklin portrait and added "USA 100" in minuscule print along a vertical security strip. Under and atop the bill's background color, he printed specks of red and blue to mimic the visible fibers woven into a real note. Illustration: James Yamasaki How to Make $100 Artist Hans-Jürgen Kuhl developed his own manufacturing process to print convincing counterfeit $100 bills. He was delighted with the final product; he felt like he'd won the Monaco Grand Prix in a Volkswagen Golf. Here's how he did it.—D.W. 1// Select and Tint the Paper Kuhl found a supplier in Prague who sold him cotton-based paper with a sheet thickness close to that used by the US Bureau of Engraving and Printing. He spent hours mixing inks in half-liter plastic cans, finally coming up with a formula to tint the paper: roughly 83 percent white, 15 percent yellow, 1 percent green, and less than 1 percent black—"for that tiny hint of gray," he says. Illustration: James Yamasaki

Kuhl's counterfeiting career had begun a decade earlier, at Cologne's Café Cento. Together with other members of what he thought of as his gang, he would spend afternoons there, eating pastries, smoking, and talking about the good old days of fast cars, drugs, gambling, music, girls, easy money—and the energy they once possessed to keep up with it all. They referred to one another and their associates with mobsterlike nicknames: "the Belgian," "the Smiler," "the Traveler," "Mr. Special," and "Manni," for Manfred Agne, a former jockey whose belly had become so large he looked like he'd eaten another jockey.

Kuhl, known as "the Dove," occupied a strange position within this milieu of part-time crooks and schemers. He was like them in that law-abiding people tended to bore him, and the idea of settling down with a family was of zero interest. But he was an artist and tinkerer, not a smuggler or thug. He first began painting when he was 10, and one of his favorite pastimes was visiting Cologne's Ludwig Museum to view its stellar collection of works by pop-art masters like Roy Lichtenstein, Jasper Johns, Robert Rauschenberg, and Andy Warhol.

Kuhl is tall, with hazel eyes, a prominent nose, and a scar over much of his right eyebrow. He wears his shirts buttoned up and tucked into jeans cinched with a leather belt. Long before becoming a counterfeiter, he had gained both notoriety and financial success. In the 1960s and early '70s, he designed and made leather hot pants—the short shorts were such a hit that he was soon running a thriving fashion business, employing half a dozen people and making enough money to drive a Porsche, jet to Majorca on a whim, and hobnob with Europe's upper crust.

In those days he was interested in various printing techniques, including silk screen, but he didn't realize how captivating the medium could be until he saw his first Warhol. "I was like, 'Wow! So easy but so different!'" Kuhl says. On a technical level, however, he found the work lacking. When he saw Warhol's Flowers, for example, he thought: "Give me four days and I could do that. Better, even. I wouldn't use so much pink."

Before long he was producing Warhol imitations, and by the early '80s he was making something of a name for himself with prints that closely mimicked Warhol's Cologne Cathedral, Flowers, The American Indian, Mao, and other images. A German newspaper once dubbed him the Warhol of Cologne.

They weren't counterfeits—Kuhl signed his own name—more like high-end knockoffs. They sold well at galleries throughout Germany and beyond. He remembers one potential customer, perhaps 25 years ago, offering him a million deutsche marks—worth about $400,000 at the time—to do two Warhol copies, including forged signatures. Kuhl refused. It went against his artistic principles.

But long-term financial security eluded Kuhl. He liked to party and seemed constitutionally unable to plan past the following Saturday. He had shuttered his fashion company (he says he got bored with it) and owed money on his car and apartment. Changing consumer tastes also hurt his business in fine art prints. Buyers were becoming less willing to spend a few thousand dollars on something that mimicked Warhol or the other artists Kuhl dutifully emulated, like Patrick Nagel, famous for the 1982 album cover for Duran Duran's Rio.

By the late '90s, as his money troubles mounted, Kuhl was suddenly presented with a chance to fix things. A man named Edgar, an associate of Kuhl's Café Cento gang, had arranged a deal with some Swiss bankers—something to do with Saudi businessmen. Kuhl didn't know the specifics and didn't much care. What mattered was the promise of nearly $100,000 in exchange for printing $5 million in half-decent fake US currency. He thought: "I could really be free again to do whatever I want," like finally open his own gallery.

In 1998 Kuhl took out a loan to buy a used Heidelberg GTO 52 offset printing machine for 127,000 deutsche marks (about $71,000). Then he bought huge sheets of high-quality paper, began mixing inks, and got to work producing what would turn out to be his warm-up run at the $100 bill.

It was an enticing technical and artistic challenge for Kuhl, and he brought an exacting obsessiveness to bear on the work. Within six months he had produced the requested $5 million. Unfortunately for Kuhl, his artistry was for naught: The deal turned out to be a sting set up by German police, and in 1999 he and a few others were arrested. Kuhl was convicted of making counterfeit money but released early on probation when a judge concluded that investigators may have been overzealous in their tactics, pushing the boundary between solid police work and entrapment.

After that Kuhl wanted to get back to the simpler (and legal) business of being a graphic artist. But one aspect of the bust stuck in his head: An expert witness from Germany's central bank had extolled the quality of Kuhl's forgeries. There was also something poetic, Kuhl thought, about demonstrating to the world that those coveted, almost sacred US dollars were nothing more than intricate images mass-produced on fancy paper. In a way, that point of view itself was borrowed from Warhol: "Making money is art and working is art and good business is the best art," the artist wrote in his Philosophy of Andy Warhol.

Hans-Jürgen Kuhl in his current Cologne studio.

Photo: Jaap Scheeren

In 2002, just back from a trip to Majorca, Kuhl met up with a sometime associate of his named Sinan Elshani, who was known simply as the Albanian. Kuhl began complaining about his never-ending debt. Elshani commiserated and said he knew a way for both of them to get rich: print counterfeit stamps. He was acquainted with the right people, who would not only pay for the machines and supplies but also buy Kuhl's fakes. He even promised to cover Kuhl's studio rent. Kuhl eventually agreed.

But it quickly became clear that they couldn't obtain the right inks for their fakes or make the perforations look convincing. At that point, Kuhl says, he tried to back out of the deal. Elshani told him it was impossible: The client had spent a lot of money on the equipment. Unless Kuhl could cough up 50,000 euros, Elshani said, the artist risked an unpleasant visit from members of the Albanian mafia.

Kuhl didn't think he could pull off the stamps, and he claims that Elshani told him he'd have to make dollars instead. In any case, the false start with the stamps got him thinking about ways to improve his fake banknotes. "It's just how my mind works," he says. With Elshani pressuring him to pay off their Albanian creditors, Kuhl agreed to crank up his printing press.

The majority of counterfeiters, as one federal investigator told me, are meth heads who, after three nights without sleep, suddenly get the bright idea to scan a $20 bill, bleach a bunch of $5 bills, and print the image of the $20 on that same paper. Even the most senile merchant can usually spot these shams.

But with his scrupulous craftsmanship, Kuhl placed himself among a rarefied class of counterfeiters who can produce truly high-quality fakes. They possess sophisticated knowledge about paper and dyes, and they have expertise in printing machinery and banknote security features such as watermarks and color-shifting ink.

With a cigarette in one hand and a money- marking pen in the other, Kuhl began his quest to conquer the dollar by thumbing through thick binders of paper samples. Money-marking pens draw a black line on paper made with starch but not on stock that lacks starch, such as the ultrafine cotton-linen sheets manufactured by Crane & Co. of Dalton, Massachusetts, the sole provider of US dollar substrate. He contacted a dealer in Düsseldorf, hoping to buy some of Crane's special blend of 75 percent cotton and 25 percent linen, but he was told that selling it was forbidden. Eventually Kuhl connected with a dealer in Prague who supplied him with starch-free paper that felt and weighed about the same as the Crane's.

Kuhl's intricate production process combined offset printing with silk-screening (see "How to Make $100"). The hardest features to forge with any level of sophistication are on the front of the note: the US Treasury seal, the large "100" denomination in the bottom-right corner, and the united states of america at the top. Real US currency is printed on massive intaglio presses (intaglio is Italian for engrave). The force with which the presses strike the paper lying over the engraved steel plates creates indentations that fill with ink, giving the bills a delicate 3-D relief and a textured feel. Its absence is a telltale sign of a counterfeit. For Kuhl this was the most critical puzzle piece: how to create that texture convincingly without the benefit of actual engraving. "I had an idea," he says, "and I was itching to try it."

His idea was to apply a second layer of ink, creating sufficient relief to mimic intaglio-pressed paper. But looking under a microscope, Kuhl saw that this second coat slumped as it dried, giving the image a blurred appearance. This problem stymied his progress until he read about UV-sensitive clear lacquer, which dries instantly when exposed to ultraviolet light. That, he says, was when everything clicked. "The ink wouldn't have time to slump," he says.

He ran a sheet of paper through the silk-screen press again, this time applying the lacquer and then drying it under UV light. "You don't see the UV varnish—that is the key. You only feel it," Kuhl says. This invisible coating atop the raised US Treasury seal and large "100" in the lower-right corner of the bill was his masterstroke. One official told the German news magazine Der Spiegel that Kuhl's dollars were "shockingly perfect."

His method may have been ingenious, but it was excruciatingly slow. Working to a soundtrack of the Rolling Stones and Dave Brubeck, he spent the better part of two years wearing white latex hospital gloves and breathing chemical fumes. He couldn't even open the windows because he worried that neighboring businesses would see or smell something that might cause suspicion. At times he would tell himself, almost as if in a trance: "Ich muss meinen Dollars machen" (I must make my dollars).

Then there was the problem of the huge amount of wastepaper that piled up around the studio—an unavoidable result of the printing and cutting process, made worse by Kuhl's perfectionism and suboptimal gear. There was far too much paper to simply shred and recycle or throw away, and to destroy it in an acid bath would have required expensive industrial-scale equipment. He couldn't burn it, either; a tower of smoke would have drawn the fire department. So Kuhl decided to bag the shreddings and take them to an incineration facility.

Kuhl idolized Andy Warhol, whom he met at an exhibition in 1985.

Photo: Jaap Scheeren

On September 25, 2006, a sorter at a garbage and recycling center in Cologne saw something odd: a torn blue plastic bag overflowing with shredded paper bearing the unmistakable pale-green coloring of US currency. There were another six bags just like it, and when the worker opened those he saw more of the same. His boss contacted the local police, who quickly handed the case over to Germany's Bundeskriminalamt, or Federal Criminal Police, which is a bit like the FBI, Secret Service, and Department of Homeland Security all rolled into one.

When he saw the mountain of shredded paper, FCP investigator Martin Becker wasn't worried that people in his country might be undermining the integrity of one of the most trusted currencies in the history of money. Instead he thought: "Oh God. This is going to be a ton of work." (Becker is a pseudonym. FCP officials agreed to let Wired interview the investigator on the condition that his real name not be published.) "The rule of thumb with counterfeiting is that wastepaper and other materials represent about 10 percent of the volume of the fake money in production," Becker says. Based on the amount of shredded material picked up at the disposal plant and later, after tailing Kuhl when he made another drop, authorities estimated that this operation had produced around $30 or $40 million in fake currency. Kuhl's lawyer, Marco Heymann, says no one truly knows how much Kuhl made and destroyed: "I don't even think he knows."

Becker was the lead agent on the case. The 42-year-old looks nothing like a G-man: leather jacket, gold ear stud, skinny Euro sneakers, messenger bag, and a diagonal scar on his forehead. Becker's team dubbed the investigation Operation Jigsaw.

Investigators set about unpacking the garbage bags and, using glue sticks, meticulously piecing together the shreddings. Within hours they found a scrap of paper in one of the bags with Kuhl's name on it, and before long they had an envelope printed with his address.

Because Kuhl was known to the local police, Becker's team quickly put a tap on his phone and trained cameras on his apartment and studio. Soon they were recording conversations in which Kuhl and his cohorts referred to the counterfeits as "wallpaper" or "Warhol pictures." In less than two weeks, the cops tied Kuhl to the shredded bills and to Elshani, who had been convicted on counterfeiting charges a decade earlier. Becker had his counterfeiters, but for the state to have an airtight case, he would also need evidence demonstrating efforts to sell the forgeries.

The problem was, Kuhl and his partners couldn't make a deal with anyone. It wasn't for lack of trying—a sale brokered by a criminal-minded former cop fell through, and another transaction with a supposed buyer in Majorca fizzled. That was when Becker and his colleagues decided to help things along by providing an attractive buyer themselves.

One afternoon in the winter of 2007, Kuhl received a call at his studio. The large, almost cavernous space was perhaps 5,000 square feet, with huge shelves running down the middle, printing machinery toward the back, and a black leather couch next to a desk. The woman on the other end of the line said she'd seen his work at a gallery in Düsseldorf and wanted to commission a new piece. Could they meet at his office sometime?

She stopped by Kuhl's studio and sat down on his couch. Kuhl guessed she was about 28 and probably of Indian descent. "Wow," he says. "She was amazing. Better than your Hollywood Jennifer Lopez or anything."

The woman explained that she wanted him to create a print for a banker in Delhi. To show Kuhl what she had in mind, she handed him a few Indian banknotes. That in itself didn't seem especially strange or suspicious to Kuhl. After all, like Warhol, he often used paper money as the subject of his artwork. When Germany switched from the deutsche mark to the euro, for example, he had made a huge print depicting a zoomed-in portion of the legacy banknote.

For the banker's gift, Kuhl came up with a bright-orange collage-style image: a mashup of elements taken directly from scans of Indian paper money, the most prominent feature of which is the spectacled visage of Mohandas Gandhi. But when he called and left a message saying that the piece was ready to be picked up, he got a call back from a woman named Susann Falkenthal. She said that the buyer was swamped with work. Would he mind if she picked it up instead? Kuhl didn't, he said, as long as she had the money to pay for it.

Kuhl was impressed by Falkenthal; Jennifer Lopez isn't really his type. She told him she thought the print was fantastic. He was flattered, and before long he found himself telling her about the challenges of counterfeiting. Listening in on their conversations, Becker and his team were surprised at how easily Kuhl trusted Falkenthal. In reality, part of him had to wonder if she wasn't bait sent by the authorities. But Kuhl had taken the precaution of having a friend stop by the address of her event-planning business, and it appeared to be on the level. "I'm stupid, but I'm not an idiot," Kuhl says. Whatever misgivings may have remained he managed to dismiss.

Then again, Kuhl was probably inclined to downplay his suspicions if it meant his beautiful creations would finally enter the great ocean of circulating cash. "It is also very likely that I did it because I was constantly being told that I was the only person far and wide who was able to make really good counterfeit dollar bills," he later wrote in a statement to the court. "In retrospect, I must admit that at least from an artistic perspective this both flattered and challenged me." If he couldn't move his product with the help of someone like Falkenthal, Kuhl knew, his banknotes would rot in a storage locker, nullifying his artistic achievement.

After Kuhl met with Falkenthal that afternoon at the outdoor café to finalize their deal, he drove with his old pal Manfred Agne to a run-down storage facility in a blue-collar neighborhood on the outskirts of Cologne. The partners had stashed the counterfeits in unit B4, next to an overturned wheelbarrow and piles of scrap wood. They packed up the notes and then headed back to the studio, where Falkenthal was to meet Kuhl at 1 pm the next day.

>Kuhl was headed to prison. But he had packed a duffle bag with some essentials, just in case.

When she arrived, Kuhl was waiting for her. Their greeting was uneventful. So was the exchange: She handed him a light-blue shopping bag with the 533,000 euros in it, and Kuhl began loading boxes of his $100 bills into Falkenthal's car. Then Becker's men were suddenly everywhere. Falkenthal was whisked away, and Kuhl was headed to prison. He had prepared for this, just in case, by packing a duffle bag with some essentials—a toothbrush, change of underwear, a few jazz CDs.

The prosecutor offered Kuhl's lawyer a deal that—considering the circumstances and the defendant's prior counterfeiting offense—was hard to refuse. Kuhl would serve six years for his crimes. In total, Becker and his team seized $16.5 million in fakes, and they are confident that was everything. (In the years since the conclusion of the case, no Kuhl-series C-notes have surfaced, suggesting that the authorities did actually get everything.)

During the proceedings, the prosecutor took the time to mention that no other printer in the world could do what Kuhl had done. He was an artist gone astray, and that, plus the fact that he was 65, convinced the state that six years was sufficient punishment.

On a chilly September morning, Kuhl and I make our way to the Ludwig Museum next to the Cologne Cathedral, just uphill from the Rhine. Only a few weeks remain on his sentence; his six years were reduced to four for good behavior. It wasn't exactly hard time. Kuhl served in an "open" prison, which basically meant checking in at night like a boarding-school student and tolerating unannounced visits from a parole officer at his studio.

We buy tickets and head toward the pop-art collection. Kuhl, wearing a black-and-white checkered flannel shirt and black jeans, walks with his hands clasped behind his back. Before long we come to the Warhols. "He was a real businessman," Kuhl says, staring up at the huge silk-screen portrait Most Wanted Man No. 7, Salvatore V. and a series of large prints of Flowers. As usual, Kuhl is dismissive of the series: "They're shit. The colors are no good. That one on the left—it's OK." He does admire Two Elvis. Pointing to black splotches on the Elvises' left hands and knees, Kuhl says, "I like the deliberate errors. It's Warhol. But I would do it clean."

Then we get to 80 Two-Dollar Bills, Front and Rear. Warhol's splotchy, bright, single-sided prints don't look anything like authentic banknotes, and Warhol never tried to convince anyone that his dollars were legal tender. Kuhl brushes aside such fine distinctions and, although he makes no pretense of innocence, chafes at the fiction of paper money's value and the riches some artists have earned by taking money itself as their subject. Warhol copied currency, and his prints are now priceless. Kuhl copied currency, got busted, and is now broke.

For the record, he denies any interest in getting back into forgery. He's doubtful he'd ever make any profit, and besides, he's nearing his 70th birthday. What he really wants is a simple vacation someplace sunny. Someplace he could maybe even quit smoking. Meanwhile, for the first time in 20 years, he's painting.

Yet later, over a slice of cake and a cigarette at the museum café, he confesses that he sometimes wakes up wanting to make just one more $100 bill. "But perfect this time. You could take it to a bank, show it to the US Secret Service, anyone—they would say it's real. That's what I want, you know? I can't explain it. It's stupid," he says with a bemused shrug. "But it'd be my Oscar. And then I could just tear it up."

Contributing editor David Wolman (@davidwolman) is the author of The End of Money: Counterfeiters, Preachers, Techies, Dreamers—and the Coming Cashless Society.