14-year-old Jimmy Bozart was out collecting the weekly 35¢ subscription fees for the Brooklyn Eagle newspaper along his delivery route when he received a handful of change at 3403 Foster Avenue in East Flatbush. As he was walking down the stairs, he dropped the coins and found that one nickel had split in half, with the front and rim of the coin rolling a few feet away. Amazingly, when Jimmy found the thicker side of the coin, a small piece of microfilm was still hidden inside it, but the shrunken sheet of numbers was far too small to read.

After taking the coin home, Jimmy thought to tell a girl in his eighth-grade class about the find and see if her police detective father would know anything about it. The coin quickly made its way to the FBI Laboratory in Washington D.C., but the Hollow Nickel case would stay a mystery for the next four years.

Upon inspection, the coin was crafted from two different nickels, with a 1948 face and a back from between 1942 and 1945. Hidden in the "R" of "IN GOD WE TRUST" was a small hole that would allow a pointed device to pry the coin open. Only a small amount of the interior had been milled down, so the coin would retain as much of its original weight as possible. When magician supply shops were interviewed to try and locate the source of the coin, they said it would be of no use to a magician, as the interior was too small to conceal anything more than a thin slip of paper.

The women who had given Jimmy the nickel as payment had no idea what it was, and seemingly no further information as to where it had come from, and the film inside proved too difficult to decode. Other hollow coins in the FBI's archives did not match the tool marks on the coin found in Brooklyn, and even the typewriter used to type the original sheet of numbers did not match any known to the FBI.

The case dragged on until 1957, when a former spy walked into a U.S. embassy in Paris and began telling a story that would unravel a spy ring operating in the United States.

Reino Hayhanen had taken on the identify of an Idaho man who had relocated to Estonia. After years of studying English and obtaining fraudulent documents, Hayhanen settled in New York in 1952 and began spying for the Soviet Union. He would meet with his superior officer in the Prospect Park subway station and exchange data at pre-determined hiding places, like a lamp-post in Fort Tyron Park and an iron fence at the Macombs Dam Bridge. In the Prospect Park subway station, FBI agents found a hollow bolt hidden in a set of cement steps that contained a small note about a meeting. Hayhanen said the Soviets had supplied them with hollow pens, pencils, bolts, and coins, including a Finnish coin found at Hayhanen's home in Peerskill, NY that was very similar to the hollow nickel found in Brooklyn. Hayhanen was also able to provide the FBI with information on how to crack the coded numbers found in the hollow nickel.

Although the message was found to be little more than a congratulations letter, the information Hayhanen provided to the FBI led to numerous arrests and the discovery of a Soviet intelligence officer and photographer whose studio at 252 Fulton Street contained a multitude of spy gadgets and decoding information. Hayhanen had apparently spent the hollow nickel years earlier and sent it on a journey that would end at the FBI Laboratory.

As for little Jimmy Bozart, by 1957 he was 18 years old and finishing his first year at Rensselaer Polytechnic Institute when he arrived home to news reporters after the spy ring had been taken down. For turning over the nickel, he received a civil commendation and even a new Oldsmobile from an anonymous businessman.

If you're wandering Brooklyn looking for your own hollow nickel, you may find yourself in Boerum Hill at the Hollow Nickel bar, which took its name from the mystery case. And, if you're looking to pass along some secrets of your own, you can order a modern-day hollow nickel on Amazon designed to hide a MicroSD memory card or an accurate replica of the 1953 hollow nickel from spy-coins.com.