After raiding a home and business owned by someone suspected of loyalties to a banned Muslim cleric, police listed the incriminating evidence they found: two shotguns, a pistol, ammunition, a fake identity card — and three $1 bills.

The serial numbers, they noted, all began with the letter F.

In one of the odder twists in Turkey's failed July 15 coup and the subsequent crackdown, authorities are citing U.S. banknotes — and $1 bills in particular — as evidence that people are followers of Fethullah Gulen, a U.S.-based Muslim cleric whom Turkey accuses of orchestrating the coup. Gulen, whose broad but secretive movement runs schools, charities and businesses across the globe, denies any involvement.

"There is no doubt that this $1 bill has some important function within the Gulenist terror organization," Justice Minister Bekir Bozdag recently told the A Haber television channel. "Prosecutors are asking as they investigate what these are. What does this mean? Why are they being carried? Does it signify a hierarchy to them? Is it some sort of ID that identifies them to one another?"

The minister said he had received information speculating on the banknotes' significance, "but contrary information may also surface, so I don't want to share it at this moment. This will be clearly revealed once the investigation is complete."

One idea making the rounds in Turkish news media is that the letters at the start of the banknotes' serial numbers correspond to ranks in the movement. According to a report in the Aksam daily, one theory is that F designates a high-ranking soldier or police chief; J and C represent low-ranking soldiers; E and S are for instructors and academics in Gulenist schools and B is for students.

"With one American dollar, this organization turned the children of this country into monsters," Prime Minister Binali Yildirim said Thursday in a speech.

A senior government official said "multiple" people questioned for suspected participation in the abortive military coup told prosecutors they received $1 bills from superiors within the Gulenist movement.

"They were told that Fethullah Gulen himself had blessed the banknotes," the official said, speaking on condition of anonymity because he was not authorized to discuss the matter publicly. Authorities' initial assessment, he said, was that the cleric's movement was using the banknotes "to simulate a physical connection with Fethullah Gulen."

The investigation is looking into whether specific banknotes were being used to send messages or designate the rank of the holder, the official said, adding that authorities believe the movement "uses an extremely cryptic language to operate secretly."

The banknotes discussion comes in an atmosphere of swirling speculation about Gulen, his movement's reach and whether or not he was truly behind the putsch.

President Recep Tayyip Erdogan has vowed to eradicate his former ally's movement. Authorities have detained or arrested about 18,000 people in a post-coup crackdown, mostly from the military. Nearly 70,000 have been suspended or fired from the judiciary, education, health care, the military and the news media on suspicion of links to Gulen's movement.

Debate over who was behind the coup has led to a frenzy of theories, from the circumspect to the outlandish.

Ankara Mayor Melih Gokcek suggested Gulen used genies to control the minds of his followers.

Internet pundits note a Gulen-affiliated newspaper ran a television advertisement exactly nine months and 10 days before the coup, showing a city while an air raid siren sounds and then cutting to a smiling baby — with pundits suggesting the ad was a secret message setting the coup date.

One Turkish television reporter was lambasted on social media after excitedly showing a notebook from material thrown out by alleged Gulenists, which listed what she thought were coded messages between coup plotters with words like "weapons" and "helicopters."

She hadn't noticed the handwritten scrawl across the top: "GTA IV - cheat codes."

They were codes for the popular Grand Theft Auto video game.

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Cinar Kiper and Ayse Wieting contributed.