He said that five other men worked with him there, from 8 to 5, with an hourlong break for lunch. Attention to detail was required, and quality control was important. Julio would mix inks in different ratios, he said, and they would run tests to get the colors right. Although he was caught and spent six years in prison in the 2000s, Julio went back to counterfeiting because he couldn’t get a job in the printing industry. Employers were nervous about hiring him. “You get stigmatized,” he said. After he was arrested again in 2018, he stopped counterfeiting and began collecting intelligence for law enforcement.

I asked Julio, a genial man with dark-rimmed glasses who is now in his 70s, how counterfeiting in Colombia had changed over the decades. When it first started, he said, the skills needed to produce high-quality counterfeit currency were held within certain families who dedicated themselves to the craft. Now, advances in digital printing had made it easier for others who didn’t have the benefit of generational knowledge to try it. Most of the veterans were dead, he told me, but a younger crop of counterfeiters had taken their place. “Every day, every day,” he said, “they are forming new groups and trying to start new plants.”

In May 2024, several months after the raid at the farm, Prieto and his colleagues shut down another counterfeit plant in the town of Villavicencio in central Colombia, roughly 380 miles northeast of Caldono. They seized about $500,000 worth of $50 bills. The notes were identical to the ones they found in Caldono, as were the lithographic plates discovered at the site, which was camouflaged as a real estate company. Pereda told me he was “ecstatic” when he saw the evidence from the raid: Now he was optimistic that the investigators were closer to finding the artist.

Prieto’s team had in fact been homing in on a suspect — a man whose number had surfaced in the phone contacts of the Ecuadorean woman arrested in Caldono. The investigators had learned that the suspect, who went by the nickname Ysraeli, was a graphic artist.

When I visited the U.S. Embassy in Bogotá one afternoon, Pereda, a square-jawed man with a goatee and an air of unflappability, ushered me into a conference room inside the offices of the Secret Service to show me what was special about Ysraeli’s counterfeit $50 bills. “One of the common ways of people telling if a note is real is they’ll run their fingernail against the president’s portrait and they’ll feel a texture,” Pereda told me. Although the bank notes in Caldono had been forged on a lithographic offset press, the counterfeiters had reproduced the textured feel by layering a special kind of ink on the note using an inkjet printer. Moreover, the notes had sequential serial numbers on them, as genuine dollar bills do. “That’s a nice feature,” Pereda explained, “because most counterfeit has the same serial number over and over on all the notes.” This, too, was made possible by combining inkjet with offset printing: Using a computer program, the counterfeiters could easily generate different serial numbers to print on every note.