The unidentified hijacker known as D.B. Cooper leapt from a commercial flight in November 1971 with a parachute and $200,000 in ransom money after threatening passengers and crew with a bomb. He was never located, although that’s not quite the same as having disappeared: Cooper became a folk hero, with both the FBI and curious amateur investigators sifting through scarce evidence for well over 45 years.

Last July, the FBI officially closed the case, citing a lack of promising leads, but continued to solicit public information if that information was compelling. The invitation appears to be paying off: A team of scientists in Seattle has recently extracted some intriguing new clues from the clip-on tie Cooper left behind.

Tom Kaye, spokesperson for a group called Citizen Sleuths, told King5 News that an electron microscope has identified several rare earth materials on the tie, including Cerium, Strontium Sulfide, and pure titanium, a cluster of particles that individuals would only have been exposed to in 1971 in very specific lines of work.

One of those lines of work is aerospace, a major industry in the Northwest. Kaye believes it’s possible the elements would have been found at Boeing during work on a Super Sonic Transport plane in the 1960s and 1970s. If the man who became known as Cooper was employed at Boeing, his tie could have been collecting debris from the workplace.

“The tie went with him into these manufacturing environments, for sure,” Kaye told King5.com. “He was either an engineer or a manager in one of the plants.”

Kaye and his team have been working on the case since 2009. Various hypotheses have been put forward about Cooper’s identity, including one surprisingly sound argument that he (or she) was a woman in disguise. Kaye is inviting anyone familiar with Boeing in that time period, or familiar with the materials found on the tie, to come forward with any information that could further aid in the famed hijacker's identification.

[h/t King5.com]