It was the most popular counterfeit $100 bill in circulation, and for more than a decade its makers were a mystery to the U.S. Secret Service.

Agents collected and analyzed the fake greenbacks, which first popped up in Israel in the late 1990s. They were so good that they were often discovered only after they reached a bank or the Federal Reserve.

So when Secret Service agent Adam Gaab came across four of the fake $100s on May 17, 2012, shortly after they had been detected at a Loan Max in Northern Virginia, he knew he had the rare chance to link a bill back to the person who passed it.

"It was the No. 1 note," said Ed Lowery, special agent in charge of the Secret Service's criminal investigation division. "You aggressively run out leads on the No. 1 note."

The investigation evolved into a two-year international odyssey that culminated in the indictment last week of 13 Israelis and Americans of running one of the most successful counterfeiting operations in U.S. history. Hundreds of agents were involved by the time they executed raids and arrest warrants in five states in May and June that resulted in the capture of the 13 suspects and the seizure of $2.5 million in fake bills and a printing plant in a Cherry Hill, New Jersey, warehouse, according to federal authorities.

The counterfeiting ring was responsible for producing at least $77 million in fake bills, mostly $100s, said U.S. Secret Service Director Julia Pierson.

Over the years, the Secret Service's forensic analysis linked 17 different versions of the fake $100 to the same source, according to court records and interviews with Pierson, Lowery and other agents.

Agents identified the ringleaders as two Russian-speaking Israelis: Itzhak Loz, 46, and Ronin Fakiro, 45. Loz and Fakiro, who have been in custody since their arrests in May in New York, made hefty profits on the sale of their bills for 20 percent to 50 percent of their face value, according to the agents and court papers.

To read the complete article, see:Fake $100 Bills Eluded Detection With Rare Quality(www.bloomberg.com/news/2014-08-11/fake-100-bills-eluded-detection-with-rare-quality.html)